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Raphael gasped as he woke, his body clenching slightly at the sudden awareness before he groaned and rolled and--WHAM!

The ground rushed up to meet him and he landed hard on his shell, finding himself thoroughly dazed and shaking his head to try and clear his vision. Something was still clouding his mind like a thick fog. His tongue felt numb in his mouth and the rest of his body was caught between an icy chill and a thrumming heat, his skin both overly sensitive and itching to be touched.

Groaning again, he pushed himself forward and stumbled as he tried to stand up and ended up several more feet further, his feet and hands oddly cold on the hard concrete floor. He grumbled to himself as he stood unsteadily, still trying to shake his mind clear. As he breathed in and out, the air around started to feel less... clogged, and his sight slowly began to even out. He stepped towards the light of the entrance, breathing heavily and trying to remember what had happened.

A moan from behind him made him turn to look and he squinted at the sight and then gasped as he realized what he was seeing.

Two turtles were splayed out on the makeshift operating table. One was Donnie, his purple bandana trailing still wrapped around his head. He had his arms spread over the plastron of the other turtle and was drooling slightly, eyes closed as he rested his head on the hard surface of...

... of_Casey'_s plastron.

The memory crashed into Raph's consciousness like a freight train, and he gripped the side of a storage bin next to him to keep steady.

The experiment.

The mutagen.

Casey's transformation.

That wave of... intense arousal.

His body flared again, and he felt like he was going to be sick for a moment before it passed. But he realized that the feeling was different. It wasn't nausea but... it was more like his body was craving something.

Badly.

There was an itch he didn't know how to scratch, like he'd eaten a full meal but was still starving. Part of him wanted to take his dick in his hand and jerk off ravenously, but another part was crying out for logical thought.

He balled his hands into fists and held them up to his head, putting pressure on his skull as he groaned with unease. That feeling of tension released ever so slightly, but it was enough for him to gain ground over his baser instincts. With a sigh, he stared over at his brother and his boyfriend.

Holy shit, Casey has to be as big as I am. But what... happened?

Taking a step forward, he squinted his eyes again. There was something in the air around the two of them. It was almost like a nearly invisible haze, slightly discolored in the most subtle shades of purple and red and pink. It caught under the harsh medical lighting Donnie had set up for the experiment and looking at it now, seemed centered around the two of them.

Was I breathin' all that in?

Casey's dick was still fully engorged, the damp, green pole throbbing in time with his heart under the weight of the other turtle's hand. Streaks of thick cum had landed all over Casey's body and Donnie's face during their mindless, almost instinctive sexual high.

Raph's throat went dry at the sight and that needy feeling coursed through him again like a buzzing hunger. It spiked inside him, and he felt the need, the _want_to lick their bodies, to fuck, to fight.

It took Raph biting his tongue hard before he could see straight again.

Donnie stirred slightly and moaned, rubbing his face against Casey's plastron, and shifting his weight on the table slightly as his legs trailed off the edge. He nuzzled Casey's dick with his snout softly and dragged his hand down through the lines of still wet cum on his plastron.

Raph acted.

Taking a quick, deep breath in, he rushed towards Donnie and grabbed him, pulling his leaner brother off of Casey and back from the table. The taller turtle squirmed in his grasp and then his eyes slowly open and a dumb grin spread across his face.

"Hmhm Raphie, y'don't need to be so eager. If y'wanna fuck me, just lay me down and... and do..."

His eyes fluttered closed just as Raph stopped about 15ft away from the table, cradling him in his arms. He released his pent-up breath and nudged Donnie in his arms softly.

"Don. Donnie, y'gotta wake up, bro. M'not sure what's going on but somethin' happened to Casey," he said, voice shaking slightly as his mind reeled.

"Donnie,c'mon!"

The turtle groaned and moved softly before his eyes shot open and his body went stiff.

"Raph? Raph, what--"

Raph breathed a sigh of relief and looked down at his brother, "Don, somethin' went wrong with Casey. He's... he mutated. But then somethin' else happened too. I can't... I don't know how to explain it. S'like the air around him is different."

Slowly, he let Donnie down onto his own two feet. Raph held his brother's hand as the other turtle wobbled, unsteady on his feet for the moment. He could practically feel the strength returning to his brother, so he let go of his shell, watching Donnie survey the room. The genius turtle was studying everything, rapidly formulating a plan of action as he always did.

Donnie glanced down at his hand and looked at the streaks of thick, white cum that coated it.

"We... I have contingencies for this. N-not this_specifically, but for if he mutated. I need to--_we need to isolate this room if there's something in the air. Can you lock the door?" His voice wavered for a few moments, but he seemed to be recovering quickly from whatever was in the air around Casey.

Raph grunted and moved quickly, walking to the entrance of the lab and grabbing hold of the door.

"Yo Raphie! We brought Master--"

Donnie shouted to him as he took a step towards Casey slowly, "Close it now, Raph!!"

Raph shut the large metal door and slid the lock in place. It was one of the few doors in the lair that couldn't be opened from the outside, mainly because Donnie needed peace and quiet from Mikey when he was working. As a courtesy though, he'd wired an intercom system for emergencies. A few seconds later, Leo's voice floated through the lab.

"Uh... Raph, what's going on?"

Donnie flicked his wrist computer and scanned the room until he spied a box of empty glass cylinders. Speaking aloud as he walked, he took one of the glasses and a nearby swab and gathered as much of Casey's cum from his hand as he could and dropped it into the vial.

"Leo, Casey's been mutated." Donnie said bluntly, his voice even and clipped as he explained the situation. "Right after you guys left the room, he started to change. But something else happened and we can't--I'm not sure if whatever it is is harmful or not. I'm locking down the lab until I can figure this all out."

He twisted around to face the door.

"Master Splinter, are you there?"

A few moments later Splinter's voice came through the speakers.

"Yes, my son."

Donnie nodded, "Alright. I'm turning the air circulation system off but I don't know if whatever happened in here got through the filters and into the rest of the lair or not. As a precaution, I'm going to have Leo and Mikey take you topside to April's apartment. The sun set two hours ago so the roofs should be the quickest and safest route there. Do you all understand?"

There was silence for a moment, but Raph could hear muffled talking from the other side of the thick metal door. Leo wouldn't be happy but he knew when Donnie was serious, and if Splinter was at any kind of risk, there was no questioning his orders.

Leo's voice answered, "Got it, Donnie. Should be there in about 20 minutes or so. I expect an update when we arrive."

Donnie grimaced and nodded.

"You'll have one."

Raph turned to Donnie who was staring over at Casey, still laid out on the table within the haze. He could see the gears turning in the genius' head as he considered their options for a few moments.

"Alright."

His voice was assured now, steady and confident as it always was when he was in the zone, "We've got some tests we need to do that will help me determine what exactly it is we're dealing with, but first...."

Donnie walked in a wide berth around Casey, constantly judging his distance between himself and the cloud until he stopped at a locked cabinet. He quickly typed in a code and opened the metal door, grabbing two filtered masks and custom-made goggles.

"Put these on," he said as placed his own pair over his face, tightening the straps around his head until they were snug.

"Just tell me what y'need me to do, Don," Raph said as he stood next to his brother, anxiously watching his mutated boyfriend breathing slowly in and out.

Donnie nodded, "Let's get to work."

Everything felt... big.

Heavy.

Powerful.

Muscles corded and pulsed as blood pumped steadily through Casey's body. He groaned tight in his throat and shifted in the darkness, taking in a breath and finding it seemed to fill him up more.

It smelled stale. Stagnant.

Artificial.

How do I know that?

As the breath passed over his mouth, he could tell its flow was... weird. Even half-awake, he knew something was off. His throat was absolutely parched, bone dry and suddenly aching for moisture.

How long was I out?

Everything started to feel just slightly different as his mind began to slough off the heavyweight of unconsciousness. Nothing was the same as what his brain last remembered--his tongue was thicker in his mouth, his back felt stiffer and less flexible as he shifted, and his skin felt tough like it had baked in the sun too long. His entire torso felt... stuck in place.

Even blinking felt wrong, like his eyelids were moving differently, something shifting under them. And yet, the more he blinked, the more the space around him seemed to come into focus.

It was dark but his eyes seemed to rapidly make up the difference. Darkness became defined. Shapes fell through the shadows and details formed in front of him. The room was full of contrast now, shadowed but he could still... see everything.

He clenched his hands and a shiver ran through his body. Something was missing. He groaned again at the wrongness coursing through his brain and moved his hand, gripping the sheets someone had drawn over his torso.

Fingers. My... fingers?

His eyes flicked towards down and he lifted his arm, bringing the hand at the end of it towards his face.

It was large and missing two fingers entirely. The two that were left were larger, looking mostly human but... bigger. Wider. And green.

For a moment, his brain tilted towards disbelief, almost sliding backward for a moment, hoping that it was just a dream he could live in until he woke up again. But something else within his mind flared outward and a rush of adrenaline shot through his entire body, driving through him like a wave of electricity, compelling his muscles to clench before he shuddered and moved without thought.

Tearing the sheets off of himself, he shot upwards and stood steadily for a moment before realizing that his balance was off, the weight of his massive shell pulling back and down as he shook and twitched against his own movement, new leathery skin bunching and stretching. A flop sweat had broken out over his body and he heaved forward, instincts he wasn't used to lighting up to try and help balance his new, unwieldy weight.

He grunted and leaned forward, hand smashing into something tall and on wheels, sending it flying backward into a wall with a crash. His body followed suit, and he found himself leaning against a cool, hard slab of brick while his breathing quickened, heaving in and out while his brain seemed to cook under pressure.

I'm a turtle... I'm... a turtle...

His muscles spasmed and his breath hitched, the strength of his new body failing as he crumpled down and landed hard on his knees, though the pain barely registered. His shell scraped against the brick slightly as he leaned a bit, putting one hand on the wall and the other clenched in a fist against the hard surface of his plastron.

He beat against it, harder and harder, feeling his fist smashing against his chest like a dull sort of bell. At least it was something.

What the hell happened?

Suddenly, the room lit up with a warm orange glow. He felt something slide across his eyes as his sight adjusted to the change, and the dark details shifted into even sharper ones. Whatever had happened to him, he could see much more clearly than before.

The glow came from a series of angled lamps hanging above in a circular fashion. As he scanned around, he realized that he'd been laying on a bed of plush cushions directly under the angle of the lights above. A cart carrying an IV bag, a coil of tubing, and a bottle of water were next to him, its metal side crunched in and bent from its impact with the wall just moments ago.

He'd never seen this room of the lair before.

Looking down at himself for the first time since waking, he studied his newly transformed body in the warm glow with a hesitant gaze.

His leathery skin was a shade of green somewhere between Raph's darker coloration and Leo's lighter. He could feel the raw power and strength underneath his leathery skin, ready to strike out instantly like he was primed for fighting.

The air felt cool around him, and he shivered ever so slightly as he realized he was wearing only a loincloth.

One of Raph's. Never thought I'd fit into those.

His broad plastron slightly obscured his view of his lower half unless he bent forward a bit, which caused the thick, yet flexible shell on his back to bend slightly. His chest and torso, while covered with the thick plates of his plastron, were still able to move almost freely thanks to their segmented sections that bent and shifted. The movement was stiff but now, he could see his lower legs and feet.

Along with the changes to his hands and fingers, his feet had also shifted and grown. Gone were his five toes and instead, two thick, green digits complete with broad, flat nails were down against the cool concrete of the room. He rocked back and forth once, then twice, just to get a feel for his new center of gravity and how his feet took his weight.

Everything felt so large now, so bulky. It wasn't difficult for him to understand that the turtles lived different lives being so big, but for him to have to deal with the same issues would be... a challenge, at least until Donnie could change him back. The sheer size of his body felt like he was living in a new world completely, with the floor seemingly miles away from him, and the size of things like the cart, the pillow, even the bricks on the wall made him feel like an absolute giant.

Which I am now, I guess.

He felt a slight twitch just above his backside and he stiffened for a moment before he realized what it was. Reaching back with one hand and managing to twist more than he would've thought his shell would allow, he ran his thicker fingers over the bottom of his shell, searching for--

"Mmmffffuck!..."

He stiffened again and let out a gasp, only this time because of a bolt of foreign sensation that raced up his spine. He felt an appendage flick and twitch under his touch and he knew it was his tail.

The thick, leathery piece of skin and bone must've been close to six or seven inches long, and it gave off a level of sensitivity that bordered on raw pleasure. He guessed that there would be a lot more of that happening with his new body. With a thought, he made it twitch against his fingers, and smiled at the novelty despite the alien sensation.

He was desperate to see himself in a mirror now, but there didn't seem to be one in this room. Something about his changes made him want to run, or hide, or go back to sleep, or maybe just accept it all and blindly move forward.

For a moment, time felt stilted. Everything felt off.

Wrong.

The breath he'd taken was too large. His tongue in his mouth felt too wide. His chest was too broad and his fingers too thick. Even the eyes in his sockets seemed to see too much. His brain was struggling to overcome an onslaught of heightened sensation, navigating new nerve pathways, and reacting to its environment in ways it hadn't ever been asked to do before.

He took a deep breath and let it out, trying to calm himself. Closing his eyes, he focused only on breathing. In and out, slowly and as steadily as he could.

There were... scents that seemed to be floating in the air around him. Fragrances wrapped up with tones and emotions--all melding together to tell a story of the space. But it was strange to him, his human senses crying out in confusion as his new turtle instincts overroad them with raw information.

Sniffing, his mind was suddenly flooded with specific trails of scents, each one leading directly to the next but all tied together and forming one shape in his mind. It was as if his brain was still rewiring itself, realizing that his new senses could feed much more information to him all at once. And he knew...

...the brothers spent a lot of time in this room together.

He could tell each scent from the other, and yet they all tied together so wonderfully, so... deliciously. He felt a sudden heat flare up inside him--

A squeal of metal on metal rang out to his left and he tensed up immediately, turning to face the noise. A large metal door swung open and Casey waited, breath pent up in his large lungs for what felt like a full minute before someone stepped through the open frame.

Raph.

Casey let out a shuddering breath as he watched his boyfriend stop and stand stock still across the room to stare at him. And then suddenly, he was being crushed by the other turtle, bound up in his clenching arms and crushed even with his newer, stronger body.

"Babe..."

Even one word caused Casey uncertainty. His mouth and his tongue and his lips--it all felt too strange, too different, like relearning a language he'd once known.

But the feeling was there, wrapped up inside that single word. That scared, desperate need to be held by the other turtle.

Raphael's scent overwhelmed Casey's nose, an onslaught of the perfectly layered notes from a heady, musky sandalwood with tones of moss and fresh lake water. His mind kept broadcasting the same message every time he took a breath: safe

Raph was safety. He was family, and his body seemed to instinctively know that. Their scents were mingling together around them and, in that moment, he couldn't imagine smelling anything else but his lover's smell forever.

Shuddering, Raph suddenly pulled back for a moment, eyes flowing over Casey's face as he traced his hands over his boyfriend's bare shoulders and hard plastron.

"Yer... ya look fuckin' good, Casey Jones."

The golden-eyed turtle just stood and watched Casey, eyes boring right into his, and then Casey realized--

"We're the same height."

His voice was deeper, more full than it had been before. It still sounded like him just... more so. Raph looked lovingly over at him before shaking his head.

"That's the first thing y'think to say?" Raph nuzzled in close, pressing his snout next to Casey's.

"Gimme a minute and I'm sure I'll think of somethin' else."

He felt so warm wrapped up in Raph's touch. Everything about it was right.

Unable to resist reaching out, he wrapped his arms around the other turtle and pulled them together, tightly.

Raph grunted--actually groaned a bit--and wheezed out.

"Jesus_fuckin'_ Christ, Casey, yer strong!"

Chuckling, he pulled Raph even tighter, "Couldn't do that before. Feels...good."

A few more moments passed and Casey slowly, softly let his arms relax, though he held onto Raph's shell with one as he traced the small, softer scales on his boyfriend's shoulder with the other. The green skin under his thicker fingers felt so wonderfully textured and detailed.

He looked at his boyfriend, shaking his head, "Raph, what the hell happened to me?"

Raph looked pained as Casey asked and behind him, a deep and heavy sigh floated through the door. Casey cocked his head past Raph's and watched as Donnie, Leo, and Mikey all filed through the opening and walked up to the two of them.

Donnie stepped up and cleared his throat.

"It's... not something that's easy to explain, Casey. Can we all... let's sit down?" Donnie gestured to the cushioned space under the lights.

Nodding, Casey glanced at Raph who was grimacing a bit as they walked over to the padded floor. His fingers automatically slid between Raph's and he felt his boyfriend grip his hand tightly for a moment as he was pulled down to sit on a section of pillows. He felt his tail flick upwards as he sat, instinct saving him the pain of sitting on his new appendage.

As he waited for Donnie to start, a warm wash of the light flowed over his skin, followed quickly by a sensation of softly pulsing waves. It was almost as if he was receiving a massage simultaneously on every part of his scaly skin. He moaned softly and felt his muscles relax slightly as his body adjusted to the buzzing warmth.

"Whoa... what's happening? Where are we?"

Donnie spoke gently, "It's our basking room. Turtles are cold-blooded, and while our mutations give us a bit more wiggle room in that regard, we still enjoy a session or two under the warming lamps. It's one of the ways we've learned to relax and de-stress over the years."

Leo placed a hand on Mikey's thigh, "We try to keep this private because--"

"--It's one of the few rooms that's big and quiet enough for all four of us to fuck in!" Mikey said with his trademark enthusiasm.

"Tch. Not that that's stopped us from fuckin' around the rest of the lair." Raph snorted and shook his head.

Donnie gave a pained look and gently pleaded, "Back to the point, guys? Come on, I specifically said not to--never mind. Let's just focus on Casey, alright?"

His three brothers all nodded and he continued. With a deep breath, Donnie continued.

"I fucked up, Casey. That's what it comes down to, ultimately. There were variables I hadn't considered before the experiment that, upon review I... I should've seen more clearly and known to look for them. More precautions should've been taken and because they weren't, you got mutated."

"I'm... I'm so sorry." He looked over at Casey and held his gaze before turning it to the floor, "You're my responsibility in that lab and I--"

"Dude, it's fine. I mean, we knew this was a possibility right? I got in close with the mutagen, for fucks sake!" Casey said with a wide smile, literally now as he felt his bigger lips draw widely over his snout. "Just hit me with the retro-mutagen and I'll be good as new."

"We did, Casey."

Casey turned to Raph in confusion, and then glanced around to see Donnie and Mikey both staring at the ground, though Leo was watching him closer still.

"You... you did? Why am--"

Donnie nodded, "It was the first thing we attempted, Casey. Raph and I woke up after your transformation and... it didn't work. I tried injecting it straight into your system and your body simply ignored it. I've never seen anything like it before."

"But you said that it would work, Donnie. You... I... we talked about this 'n how it couldn't happen. It was a failsafe or fucking whatever!"

A flare of anger seemed to rip through Casey's body and he felt himself trembling somewhat as he sat there, staring across at the... scientist.

"What. The fuck. Happened?"

"It was us, Casey."

Leo's voice was calm and caring, and his expression held nothing but shame and heartbreak for Casey.

"It was us. We... all of us caused this to happen. Me, Donnie, Mikey, and Raph."

Mikey shifted slightly in on his pillow and pulled one into his lap to hold, "We shouldn't have done anything, like, _fun_fun with you before the experiment, dude."

Casey stared incredulously at the brothers and then let out a shocked gasp of a laugh.

"You're saying we shouldn't have had... sex?"

Donnie nodded slowly. Raph's hand slipped from Casey's and he watched as the big turtle bowed his head slightly and turned away for a moment, sighing heavily before turning back with a sorrowful look.

"How long was I out?"

"About six hours. Enough time for me to figure out some of what happened." Donnie said heavily, gesturing at Casey.

"The mutagen reacts wildly with any organic matter in whatever living being it finds itself. Normally, it reacts by combining trace elements of foreign DNA it can find and pairing it with the hosts' DNA, hence, someone like Master Splinter being mutated into a humanoid rat. He'd come into contact with rats in the sewers soon before being exposed to the mutagen."

"And we..." Leo spoke up, "We'd come into contact with him before we were mutated. Hence, Turtle humans."

Donnie shook his head and held up a hand, "That's a severe oversimplification but... mostly correct. There's a lot more that goes into what it does on a genetic level but that's normally how I've witnessed it react while I've studied it. But with you, it had... well, it had more than just our turtle DNA to react to."

"Because... we had sex?" Casey asked, still stunned at how that question was related to any of this.

"Yes. I took samples of your blood before the experiment and then after, and the changes were frankly astounding. Not only did the mutagen transform you into our likeness, but it fundamentally altered your genetic makeup in ways I've never seen before. You have strands from each of us woven into your genetic code now. You're essentially our fifth brother, for all intents and purposes."

"We're... related now," Casey said plainly.

Mikey shrugged, "Well hey, if you can't say you love your new brother by eating your other brother's load out of his ass, how can you say it?!"

The other four turtles just stared at him.

"Yanno like... like when you're kissin' on 'em, or fingering them in the kitchen, making 'em moan your name out loud in the lair so your dad knows exactly what's up!"

The silence was deafening.

"... You guys do know what incest is, ri--"

"--Read the room for once in your life, Mikey," Raph groaned and rolled his eyes, "Jesus Christ, dude."

Donnie sighed and continued, eyeing Casey, "You're not wrong, though. We're more family than most families. But Casey, something else was changed inside you. The mutagen reacted in a way I'd never seen before. I've theorized that there's some sort of biological artificial intelligence that the Kraang designed to make the mutagen as effective as possible in humans. If that theory holds up, I believe that that same AI is making your body resilient to the retro-mutagen by causing... other mutations to occur inside you."

Casey looked directly at Donnie, "What kind of 'other' mutations?"

"When I woke up, somethin' was different." Raph's voice seemed so small for how big the turtle was. "It was like the air around you was off, somehow. Thicker. Filled with a cloud, and it had driven me an' Donnie crazy for you."

"I... remember we uh... things got pretty heated." Casey said, feeling a blush creep up cheeks, unsure if the others could even see it under the soft, coriaceous skin on his face.

"Yeah. It was fuckin' intense. A rush and a need and like... a high all at once. Never felt anythin' like that before. I pulled Donnie away and once he was awake, we ran some tests on you."

Donnie nodded, "Your body now produces a pheromone that seems to act as a powerful aphrodisiac, released from the pores between your scales. I haven't been able to test it much but, when your body is primed for it and we get within a few feet of you, we start to feel the effects almost immediately."

"But... why? How?" Casey asked.

"If I had to guess?" Donnie shrugged and shook his head, "It's from the, uh, fluids you came into contact with from all of us. The mutagen may have reacted to them and incorporated them into your mutations, focusing on their biological reproductive purpose and infusing that same purpose into your body. Almost weaponizing it in some way. It could take _years_of study before I can dissect the millions of lines of your new genetic sequence and try to make sense of them. But that's my best theory at the moment."

Casey stared at Donnie for a few seconds, trying to parse the information in his head but felt like he was running into a brick wall. He looked at each of them, meeting their gazes before he sighed and let out a pent-up breath.

"So... am I producing it now? You all seem fine to me."

Donnie shook his head, "Not at the moment. From what I've been able to gather, your body produces those pheromones at a greater level when you're aroused. It's still produced outside of that, but the sexual high that coincides with their release isn't triggered."

Casey shook his head, "So, you're saying I can't get a fuckin' boner anymore?"

"Not exactly. You can't help if you get aroused, especially not around here with us. So... sexual intercourse is most likely going to occur, especially with our normal routines and needs."

Leo snorted and nodded in agreement while Mikey giggled. Raph swiped his thick finger over Casey's thumb softly, which was all he needed to know about what was going through his boyfriend's mind.

"Luckily, none of the dozens of tests I ran with your pheromones have led me to believe that they're in any way dangerous to us or... really to anyone. They just massively increase sexual need and desire. As I mentioned, it's an extremely powerful and very robust aphrodisiac. Realistically, it could affect any being with a reproductive system, and could possibly even be directed and used during combat to distract enemies or--"

Leo broke in, "Wait, Donnie you've actually _thought_about this!? Let's not get ahead of ourselves. Casey's not even close to being used to his mutations."

Donnie held his hands up to stop himself, "Sorry, I... there's a lot of potential. Unknown potential, which just means there's a lot to learn, Casey. And there may be more changes and mutations that we haven't seen yet. As I said, I need more time to study this so that I can figure out how to reverse it.

"But for now, I'm... a mutant turtle?"

"Yeah," Raph said, sliding a hand over Casey's and gripping it tightly, "Yer a fuckin' mutant, just like us."

His voice was still heavy with emotion but there seemed to be some pride in his tone.

Casey looked at all of the brothers in a different sort of light. It wasn't every day that the brothers found themselves another member of their species, let alone a new, biologically verified member of their family.

Mikey scooched over and pulled himself up to Casey's other side, grabbing his hand and holding it in his own.

"Luckily, we're all kinda pros at being turtles, dude. So, no worries if you have any questions about anything. I'm basically a walking turtlepedia if I'm honest."

He leaned in close to Casey's snout and whispered, "My explanations of turtle anatomy are way more fun than Donnie's. Leo and Raph can vouch for that."

"Hey, I resent that!" Donnie glared at his younger brother.

"Mikey..." Leo pinched the bridge of his snout and sighed. He glanced at Donnie and then they both moved forward to sit directly in front of Casey.

The four brothers--out of five now--sat in a close circle, all looking at their newest addition.

"We're here to help you, Casey. Anything you need." Leo spoke softly but there was a passion in his eyes as he looked at Casey, like he would find any way he could to make him as comfortable and happy as he could.

All of the brothers were looking at him with that same expression.

Love.

"I..." Casey started and then tilted his head back, a breath caught in his throat.

"Thank you, guys. Actually...thank you, my brothers, I guess."

They shared a soft chuckle for a moment and Raph leaned in, kissing Casey on the cheek before reaching out and turning the new turtle's face towards his own and capturing his lover's lips.

It was a simple kiss, though different in so many ways from what Casey was used to feeling. There was going to be so much to get used to. Raph's tongue swept lightly over his lips, teasing him ever so little.

Casey pulled away, looking at Raph with a knowing grin, feeling the warmth of the heating lamps amplified by the collective body heat of his brothers. Leaning back, he splayed himself across the pillows and closed his eyes as Mikey snuggled up along his side and rubbed his arm lightly.

"I've got more energy than I know what to do with now," Casey said softly as he stared up at the array of lights above, "But would you guys mind if we stayed here for a bit? I need some time to get... used to all this."

Raph kissed his shoulder as he sidled up to his boyfriend's other side, gently taking Casey's hand in his and placing them both on the newly mutated turtle's chest.

"'Course you can, Case'. S'why we're all in here with you. Gonna help you through this."

Donnie nodded in agreement as he laid down just under Raph, slowly rubbing his hand over Casey's ankle in a soothing manner.

Leo moved and slid his shell between Mikey's legs and settled into their pile. He reached out and placed his hand on Casey's lower plastron protectively, feeling his breath stretch the plates up and down steadily.

The lights beamed their warmth down on all five of them, a pile of turtles basking fully in the haze. Casey's eyes fluttered shut at once, the feel of his family surrounding him like a weighted blanket, and it set his mind at ease as he slipped back into darkness.

It was different from how Casey had imagined it.

Learning his new body came with a ton of challenges, not least of which was simply getting used to his sheer size. Gaining over a foot and half of height and nearly 250lbs of weight wasn't something you could just get used to overnight. For the past two days, he'd constantly hit his head on doorways or trip over the smallest of items strewn about the lair. He felt unwieldy and unbalanced with his heavy shell on his back, which was yet another part of him that seemed to go out of its way to catch on corners or knock over shelves.

He was sure that Donnie was tired of him accidentally knocking items to the floor in his lab as he continued to run tests on him every few hours, though the brainiac never let his annoyance show. All of his new brothers had been extremely gracious with him, offering pieces of what Mikey called 'Mutant Turtle 101' advice.

It came down to the little things. Learning the feel of his size and training his mind to watch out for the tiniest of details in his surroundings. He was an enhanced, powerful mutant now, and even holding something too tightly could result in its destruction, as he'd learned while trying to drink water out of a cup. One tiny twitch of his thicker fingers and it had blown to pieces.

But he was a quick study.

He hadn't anticipated being asked, but training with Leo turned out to be oddly satisfying. Splinter had suggested it, and Raph was giddy with the promise of getting to watch Casey get his ass handed to him by their fearless leader.

Leo had started with the basics, having Casey watch him perform simple katas and then repeat them. He'd moved onto a few different types of defensive moves and stances from there. In just two days of training, Leo had taken him through a crash course in the absolute basics of ninjutsu, and Casey had never felt so lost in his life--or so thrilled at the prospect of learning more.

He was a natural-born fighter, a New York City street brawler through and through. Ninjutsu clearly wasn't his strong suit, but something about the way Leo taught him made it feel natural. Donnie had theorized that it was possible some instincts from the four of them might have transferred over to Casey on some level during his mutation. Whatever it was, he felt like he'd managed to keep up fairly well with Leo in the few training sessions he'd had.

Of course, being sent flying across the dojo with a lightning fast jump-kick to the chest had instantly crushed any hopes he had of catching up to the rest of the turtles.

"You need to be aware of my feet, as well as my hands, Casey. Part of being a ninja is learning to tell where the next strike is coming from, ignoring any distractions and finding your opponent's flow." Leo spoke with the confidence of a true master, watching him constantly.

Groaning, Casey rolled to his side and stood up. Leo's kick had come out of nowhere. Impossibly fast and with the force of a freight train.

"Yeah," he grunted, shaking his head to clear it, "Well, we were kinda focusing on punches. Wasn't expecting a kick."

"S'first of many lessons you're gonna have t'learn, babe," Raph said with a smirk as he watched from his upside-down perch on a thick set of steel high bars. He curled himself up and down with a soft grunt as he returned to his workout.

Leo stood in front of Casey and nodded, "Raph's right. This isn't something you can just expect to rely on your basic instincts for. You need to create new instincts through training and discipline. If this is something you really wanna learn, then you'll be training with us every day. You'll be part of our team in every sense. Are you up for that?"

Casey sighed, shaking his head, "Look I know I'm not as precise and experienced as you guys are, but you've seen me fight before. Hell, I've helped you take down more than a few hundred Foot soldiers, Purple Dragons, and even mutants over the years and I always held my own. And that was when I was human! Imagine what I can do now!"

He heard the soft sound of feet padding from across the room and he turned to see Splinter stepping towards them, his clawed hands clasped in front of him.

"My son, we have all seen how brave and talented of a fighter you are. Leonardo is not questioning that."

The old rat stepped beside Casey and nodded at his eldest son, "What Leonardo needs to know is if you will allow yourself to be trained, to learn, and if you are willing to trust in his leadership and guidance, as your other brothers all do."

Leo stood in front of Casey with a curious expression across his face, waiting for Casey's answer. Raph curled himself up and sprung over the bars with ease, sitting atop them and watching, breathing heavily from his workout.

With a nod, Casey answered, "Of course, Master Splinter."

"Do not answer me, my son. Answer to Leonardo," he said with a gesture to the blue-masked turtle.

Casey stared at Leo for a moment.

Like Splinter had said, this is what each of the brothers had gone through at some point in their lives. Accepting that their team needed a leader and that Splinter had chosen Leo after years of watching and training them all. Casey had seen how effective the eldest turtle was at leading his brothers both in and out of battle.

But he had never been truly part of their team on the battlefield before. Never thought of himself as an equal when it came to their prowess in a fight. He'd always felt relegated to the sidekick role, not that he minded.

Now though, he had an opportunity to be central to that team, to grow their strength and change their dynamic for good.

The question was whether or not he wanted it.

"Leo... yes. Absolutely. I know I got a hell of a long road ahead, but I want to learn as much as you're willing to teach me."

Leo nodded, his expression as serious as Casey had ever seen it, though he thought he saw a hint of satisfaction playing across his lips for a moment. Raph grunted as he launched himself from his perch, landing on the padded mats and walking up to the three of them.

"Oh man, now Leo's gonna make you his pet project. Good luck with dat, babe," he said with a wink to Casey. He slid an arm around Leo's shoulders and tilted his head to one side.

Splinter chuckled softly, "Casey Jones, you are in the best of hands. Now if you will excuse me, my stories are about to start."

The rat glanced at the three of them for a moment before giving a satisfied huff and walking off towards the living room. Raph watched him leave before looking over at Casey.

"Y'know, this just means we can all kick your ass during training now. Hope you're ready for some serious bruises."

"Hey, just so long as you're all there to help patch me up after," Casey replied with a grin, before arching his brow with an idea. "And of course, you all can show me the best ways of relaxing after a long day of training. I'm sure you got a ton of know-how in that area, right?"

Leo glanced at Raph and then stepped towards Casey, bringing a hand up to his cheek and running it sensuously over his lips before sliding it down his neck. Raph crossed his arms over his plastron and watched with an eager look in his eyes.

Casey felt a twinge between his legs as Leo trailed his fingers down his plastron while simultaneously leaning in close and softly nuzzling his snout against his own. Leo's breath washed over his lips and he parted them slightly, nearly kissing him.

"Well," Leo said in a whisper as he closed the distance and pulled Casey close, kissing him deeply and sliding his tongue over the new turtle's. He pulled away slowly after a few seconds and moaned softly, "I'm glad we're all on the same page."

"Y-yeah. Me too, Le--"

Faster than his mind could process, he was suddenly flipped upside down and slammed into the ground. His breath was knocked clean out of his lungs and he groaned with what little sense he could find.

Raph was doubled over with laughter at such an obvious ploy and a more than satisfying outcome.

"Dude," he laughed, trying to catch his breath as Casey was doing the same on the ground," Dude, I take it back. _That's_yer first actual lesson. Never trust Leo during trainin'. Oh my god, Leo, it's been way too long since one of us has fallen for that shit!"

"I gotta say, it felt pretty great too. Reminds me of when we were teenagers." Leo said with a grin as he stood over Casey.

"Yeah, yeah," Casey coughed and huffed, laying on his side and looking up at his brothers. "Laugh it up, assholes. Won't happen again."

"Mm, y'just gotta look out for Leo's big, sexy blue eyes. Those things are killers." Raph and Leo reached down to help Casey up. With a groan, the newest turtle was back on his feet and looking warily at Leo.

"Yeah well, that might take a while for me to ignore. Truce?" he asked, looking at Leo.

"Truce. Until tomorrow morning, at least," Leo said with a grin.

Casey nodded and winced, "Fuck, that hurt, man! Like, that shouldn't be possible to hit that hard and fast."

Leo smirked over at him, "You'll get there. One day."

He tilted his head in thought, "Maybe."

"Nah, he will. Jus' gonna take a minute." Raph said as he slung an arm around both of his brothers. "Want me ta kiss it better?"

"Only if Leo helps. S'his fault in the first place."

"I think that can be arranged." Leo chuckled as the three of them walked out of the dojo and headed towards the kitchen, wondering what Mikey was cooking up for them.

It was nearly impossible to tell day from night in the lair. Nearly, because Donnie had timed the lights in the living room to dim according to the sun's position above ground. And as Casey walked through the wide expanse of the living room and laid down with a soft sigh on the worn couch, he stared up at the now dark lights above him.

A soft glow emanated in the kitchen from a little plug-in night light Mikey had installed, given his proclivity for late night baking. Even with the dim light from across the room, Casey marveled at his new eyesight. Colors and shadows that would've been hidden from view just a 48 hours ago were now clearly detailed and defined. It was almost eerie how well he could make out the lair, and he understood how the brothers... how _his_brothers were able to move about and see in near total darkness.

His eyesight was one thing but the scents floating about the lair were another. They colored every breath he took and fed waves of information to him that his brain instantly was able to decode. Even now, he knew just how many nights the other turtles had spent out here with each other. He knew which seats they each preferred to sit in.

He could even smell his own scent, slightly changed but still strong from he and Raph's little tryst together before the experiment.

A twinge in his groin made him frown for a moment, groaning at himself as he laid an arm across his eyes to black out his sight. It wasn't that he didn't want to think about Raph. Or Leo, or Donnie, or Mikey. He desperately wanted to let himself go. But something held him back and had been since he'd woken up.

Whatever mutation had occurred within him, he was scared to let it take control of him again, knowing that it would affect his brothers as well. What if they lost themselves to his pheromones and got hurt somehow? What if he couldn't stop himself and did something to one of them? He barely knew his own strength now, let alone his new instincts.

He sighed again and laid in silence for a few minutes. And then, Donnie's scent filled his nose and he heard the sound of wrapped feet on concrete padding over towards him.

"Can't let you fall asleep out here, Jones," Donnie said with a smirk as he stood with his hands on his hips in front of Casey.

"Jus' restin' my eyes for a minute, Don."

The tall turtle nodded as he stepped forward and grabbed Casey's legs and gently pulled them off the couch, setting himself down in their place.

"Well, Mikey and I have a date right here on this couch so, if you wouldn't mind, I think Leo and Raph might be waiting for you elsewhere."

Casey groaned as he lifted his arm from his eye and glanced over at Donnie, who was placing a custom-made headset over his skull.

"You have a date?"

Donnie nodded, fidgeting with the microphone, "Mhm. The past few years, I've really gotten into EVE Online. One of the ways I supplement our income is by running espionage and blackmail campaigns against rival corporations in the game. Made $14,000 last year."

"Of... real money?" Casey asked.

Donnie shrugged, "Bit more complex than that, but, yes. Turns out, I'm really good at bringing down groups of people from the inside with little to no violence. Who knew!"

"Yeah," Casey said looking warily over at Donnie, "Who knew."

He paused and then asked, "So... what does Mikey get out of this? Doesn't really seem like his kinda game."

"I get to suck Donnie's dick all night, dude, if you really need to know."

Mikey's voice floated in from behind them before he bounded over the low couch, then settled in the middle seat between the two of them. He carried a tray of snacks and soda cans that he easily managed to keep stable despite his movements.

"Dude, this game is great. Donnie gets super into talking to the other guys and learning all their secrets. And meanwhile, I get to... well, Donnie hasn't ever told me to stop no matter what I do, so like, I think I have free reign over him."

Donnie shrugged and Casey could see a lightening of his cheeks even in the dim lighting. It wasn't what a human would call a blush but for a mutant turtle, that seemed to be an apt description.

"What can I say, Mikey. You've got a talented tongue."

The youngest turtle beamed as he set the tray on their small coffee table in front of the couch and leaned over to kiss Donnie with a moan, running his hands over the nerdy turtle's frame.

"I uh... guess I'll just leave you two to enjoy yourselves." Casey said as he watched the two brothers press into one another. That same fire flared through his body and he tried his best to douse it.

"You uh... you said you wanted to know how things go when I, like, let loose, right Don?"

Breathless, Donnie pulled away from Mikey and leaned his head back against the cushion, "Y-yeah. But I figured you'd wanna be with Raph and, er, well Raph _and_Leo when you do."

"No, no, that's not it. I just," Casey scratched his head and shook it with a slight grimace, "I just feel kinda... _worried_about this mutation shit. I-I know you said it would be fine but--"

Donnie sighed as Mikey unlatched his lips from his neck and they both turned to face Casey.

"Case'... I promise you things will be okay. This is part of who you are now. Of what you are. It's okay to let go of yourself. You're in the safest place you could be with the only people who understand what you're going through."

"Ditto, bro," Mikey said with a grin as he softly punched Casey's broad shoulder.

Donnie looked at him, studying his face for a moment before he spoke softly.

"Look Casey, I get that this isn't what any of us wanted to happen. But it's what you have to deal with now. I say embrace it! It's not like you can get away from it anyway. If the four of us know anything, it's that being a mutant turtle comes with certain bodily expectations, and if you ignore them for too long, well... let's just say things can quickly get out of hand."

Mikey chuckled, "No joke, I edged for like two days and blew a load clear across my room. That's 25 feet, bro!"

Casey laughed, "Why am I not surprised someone measured?"

"I keep notes on everything," Donnie said with a hint of pride.

"Mmhmm." Casey smiled and nodded as he leaned forward and lifted himself up from the couch, "Well... I'll let you two enjoy each other. Guess I'll go find Raph."

Mikey snuggled into Donnie's chest as the older turtle fired up the TV and grabbed a controller.

"He's in Leo's room, my man. Think they're both waitin' on you," Mikey said as Donnie kissed his head gently, "Though they seemed to be going at it pretty hard, so I wouldn't keep them waiting much longer."

Casey swallowed dryly as Donnie winked at him, shifting his focus to the TV. With one last glance at the couple, Casey turned and headed further into the lair, his whole body buzzing and twitching with one feeling he couldn't deny himself any longer.

Need.

Leonardo's room was the furthest back in the lair, directly opposite the entrance to the dojo, which Casey assumed had been purposefully chosen. Leo always wanted to set the example for his brothers; first to rise for training and all that. It also happened to be the furthest away from Splinter's room, which he figured the brothers probably used to their advantage many times growing up.

He smirked at a memory. Sneaking himself and April past his dad's room when they'd stayed over his tiny Jersey City apartment one Christmas Eve, a few years back. How things had changed since.

Leo and Raph's scents drew him further back through the lair, his body buzzing like an old lightbulb at the anticipation. The scents shifted in tone and color as he neared Leo's simple wooden door, heating with a warmth and musk that he was all too familiar with by now. His ears could pick up soft moans and quick kisses passed between the two brothers and he bit his bottom lip, standing outside the door and listening.

"R-Raph--!"

"Mm, fuckin' god, Leo... unhh!"

Casey shuddered, a sudden clutching terror shooting through him.

He'd done this before, many, many times. But this was going to be... different. And, despite Donnie's assurances, possibly dangerous. He placed a hand on the door, eyes tracing over his three thick digits as he let his mind wander through the outcomes.

But then he heard Raph moan again. That voice... it belonged to the turtle he'd fallen for. The mate he'd chosen. And he was afraid to be with him now? No.

No.

Steeling himself, he leaned forward and swung the door open and stepped through it, letting it close softly behind him as he observed the sight laid out before him.

Leo's room was sparse, though not without its charms. It was dim, but a few candles flickered on various shelves and two cheap IKEA floor lamps glowed gently, their light casting shadows on old photos and nicknacks and pieces of armor Leo had neatly placed throughout the room. Everything looked purposefully positioned, which Casey knew Leo must have agonized over each time he added something.

The bed, centered on the far wall, was as large as Casey had ever seen. Its sheets were tightly drawn across it and a thick, gray comforter laid neatly over top, upon which Leo and Raph were sprawled.

Casey's mouth was suddenly filled with saliva at the sight of his brothers, their skin seemingly to glow under the soft lights. He felt a hunger for them both, an utter craving for what they could do to him.

Leo was settled upon Raph's lap, his thighs spread and legs bent alongside his brother's as he leaned forward to kiss the larger turtle. Raph was thrusting gently upwards against Leo's steady bouncing, moanings leaking from their kiss as he rocked upwards and slid his length into Leo's ample backside. One of his hands cupped Leo's cheek while the other was between them, gently pulling at Leo's leaking, massive member pinned between their plastrons.

The two of them were in total sync, aware of each other's needs and instantly ready to fill them at the slightest sense of want. Casey could see how well they fit together. He felt that same thrill he'd noticed in the showers, watching them all work as one and realizing that he was part of their equation now.

He was drooling at the sight, his tongue panting out of his snout and his jaw slick with pheromone-infused spittle. Tail twitching wildly, he couldn't help but feel slick and eager, his firm buttocks sliding smoothly against each other as he bounced slightly on his wide toes.

He was filled with it.

Anticipation.

Lust.

A need to be with his brothers.

Muscles seemed to tighten and his cock swelled between his thighs, hidden only by the borrowed loincloth Raph had lent him.

"Mmff--oh_shit_, C-Casey!"

Raph stopped mid-thrust and leaned back slightly from Leo, his eyes a bit wider and more cautious than anything else. Leo simply leaned down across Raph and turned slightly to eye Casey as he stood facing them.

"Hey."

His voice was... sultry.

Needy.

He stepped forward towards the pair, undoing the knot at the back of the loincloth as he moved closer, watching them watching him. His pupils were blown wide and the world seemed slower, smoother. He was able to examine each exquisite detail on his brother's bodies as he neared them; the complimentary green tones, Raph's undulating muscles tracing across his shoulders, and Leo's powerful legs continuously thrusting his body up and down on Raph's cock.

"Thought I'd better make an appearance 'fore you guys got to the good stuff."

Leo leaned back slowly with a moan as he sat up straight and watched Casey, drawing a shudder from Raph underneath him as the thick shaft bobbed freely and leaked over his brother's plastron, "I'd say the good stuff just got started, tiger."

Casey had never heard Leo's voice like that. It was deep and husky--and he couldn't help but love it. His eyes flicked to Raph's.

His boyfriend held out his hand and Casey walked the final steps toward the bed, grasping Raph's fingers in his and leaning down. Their scents were swirling around him in a heady mist of sensual fervor, and he felt his body tingling like it was attached to a battery waiting to explode.

He knew his pheromones were already started to release into the room, and had been since he'd opened the door. But now, somehow still clear headed enough to be aware of his own surroundings, he wondered just how far they would take the three of them tonight.

Let's find out.

"Raph," he said softly, looking at the other turtle as he nuzzled against his snout, "I want you. So badly. I... need this, babe. I need--I want you both. An' I don't wanna stop myself. I wanna let loose. I can't explain it but I... I fuckin' need you in me right now, baby."

Casey's voice cracked as he looked at Raph, a frantic feeling of need coursing through him. He shuddered, his own words not conveying the absolute desperation he felt. His hole was twitching, far too empty for far too long. Slick ran down his thighs as he thrusted his hips hard against Raph's side, smearing his leaking cock over his brother's scales.

Raphael reached out and pulled their mouths together, kissing him deeply. Their tongues lanced out and slid over each other, saliva mingling and tastes combining. Leo watched eagerly, still impaled on Raph's length and loving the show, his dick spurting precum and jumping up and down with his gasping breath.

"Then don' hold back, babe. Lemme see what you can do."

Casey felt the buzzing in his body turn to flame in an instant and he moaned with a shuddering passion as he attacked Raph's mouth with his own. His skin felt like it was burning with pleasure and the haze he'd remembered from his mutation began to fill the room.

But it was different this time. The haze began to surround the three of them, and instead of overwhelming them all to the point of mindless pleasure, it seemed to heighten and expand their senses. Each breath added new layers to their passion, and their hearts thudded faster in their chests, blood pumping through their veins and thickening their muscles.

Leo gasped at the sudden rush, feeling Raph's cock in his hole actually thicken and pulse as he bounced against his brother's lap, while he watched Casey shuffle slowly over the top of the other turtle. The eldest brother had enough sense to stand up at that moment, sliding off of Raph's dick and leaving himself feeling empty and hollow for a moment. But with a knowing smirk, he moved back and watched Casey straddle his mate, his ample thighs spread just like Leo's had been moments ago.

"F-fuck, babe, it's like... s'like I took a massive hit of poppers or somethin'!" Casey gasped as he kissed his way down Raph's neck and upper plastron. He'd felt Leo move and knew the older turtle was giving him the honor of sitting where he'd just been.

"N-never felt this good before, Case--" Raph gasped and arched his back as Leo reached out, still kneeling on the bed, and grabbed his cock in his hand while Casey settled over his lap, "Oh, fuck, I'm literally ready to cum right now!"

Casey wanted to laugh but he could feel his mind starting to narrow slightly, to focus solely on the turtle in front of him. He wanted to be bred. He craved it.

"Jus' hold on, babe. L-Leo, can you--oh my g-god, can you gimme an assist here?" Casey's voice wavered as his mind absorbed the pleasure it was giving, nearly unable to process the heightened experience.

Leo held Raph's cock in his hand, fingers barely able to wrap around the huge green pole as he eyed Casey's ample ass settling down over his brother's lap. Leaning forward, he watched with wandering eyes as Casey's tail flagged up automatically, revealing the tight, virgin turtle pucker underneath.

The opening clenched and pulsed, coated in a natural slick that gave off the most wonderful scent. Leo sniffed at it with a ravenous fervor, rapidly breathing in and out as his instincts screamed at him to continue. His pupils dilated and his body flared with a huge burst of raw lust as Casey's hole reacted to him, quickening its clenching and unclenching to entice the big turtle further.

Leo was utterly mesmerized by it and, before he even realized, his tongue was sticking out of his mouth as he panted with need, eager for a taste of that slick, tight entrance.

Moving forward ever so slowly, Leo licked a stripe over Casey's hole, feeling the skin twitch under his wide tongue as he tasted the delicious musk of his new brother.

It was... new. A different taste from any of his other brothers, but it was delicious. Powerful. Heady and rich in a way none of the other turtle's were. He wanted more.

Casey's body seemed to draw Leo in and he pressed his nose against the opening, breathing in that heady scent over and over as his mind reeled from utter desire--desire to taste and smell and smear his brother's musk everywhere he possibly could. He licked out again, pouring his tongue like liquid against that slickened hole and thrusting it in to get at the source.

Casey cried out as Leo's lewd, wet slurping against his entrance drove his need to new heights. His body was pulsing with every powerful beat of his mutated heart.

"Oh shit, Leo! F-fuck, your tongue!" Casey shuddered at the foreign sensation, quivering in Raph's hold as Leo lapped at his virgin hole. "Yer a goddamn _magician_with that thing, Leo!"

He grasped Raph's shoulder and leaned down to lick at his mate's neck, tasting his lover's sweat and musk as Leo ate him out eagerly. Raph turned his head and bared his neck to Casey, letting his new brother lick and nibble and bite hard at the skin, pinching the thick layer between his wider teeth and popping the blood vessels underneath.

Raph shuddered and gasped at the bite, and he felt Leo's hand automatically turning and pulling at his cock as the eldest turtle rimmed Casey deeper. Even under the influence of the mutated pheromones, Leo still remained one of the best multi-taskers, able to bring pleasure to anyone around him at the same time. He moaned loudly, lewdly as his brothers touched him. Casey's tongue was like a firebrand as it lapped across his scales, trailing a heated, pleasurable tingling sensation wherever it went.

Feeling Leo's tongue digging deeper and deeper inside him, Casey pushed back hard. Leo reached forward and pulled him tighter, thrusting his snout forward into that tight heat. He could feel Leo's saliva and his own natural slick mingling, making passage easier for the intruding tongue. It was like his backside had some sort of pleasure receptors that fired off a jolt of pure bliss at every thrust of Leo's tongue, and his thighs shuddered on either side of Raph's lap.

The three of them laid there, Leo working his magic on Casey's hole like a man possessed. Some instinct drove him to eat him out, to dig into that source of heat and essence and revel in it while Casey spasmed around him. Raph knew the feeling well and moaned loudly as Casey licked his neck, feeling Leo jerk his pole with a steady, powerful grip.

Raph pulled Casey away from his neck and thrust a finger into his mouth, instantly coating it with the same tingling saliva. Moaning and grinding his hips against Casey's, he pushed his finger deeper into Casey's mouth, leaning up to lap at his lover's neck eagerly.

Leo knew he couldn't eat out his brother forever, at least, not tonight. Raph and Casey needed to connect, and he would get to watch and guide them along, a thought that sent his own cock a spasm which painted the bed beneath him with a wave of sticky precum. Slowly, he pulled his tongue back and, with an utterly lewd slurp, out of Casey's still tight hole. He smirked at his work, the slick saliva and musk running straight down Casey's taint as his tail flagged back and forth with anticipation.

He leaned forward again, pressing in and under Casey's perineum, nudging the low hanging, overfilled balls and letting them rest on his snout. He hummed in contentment and licked his long tongue out, swiping Casey's jostling sack for just a moment before he slowly pulled back.

"I think we're ready for the main attraction now," Leo whispered, smirking at the two turtles in front of him.

Raph shuddered as he felt Leo grasping his cock, positioning it right at Casey's entrance. It fluttered rapidly and Casey drew a sharp breath at the sensation, letting Raph's wiggling finger trail slowly out of his maw and down his neck.

The edges of the room were spinning and tilting in all their visions, but the constant need and desire kept them each focused on their chosen task.

"Casey, lean back as slow as you can. I wanna... watch this up close." Leo commanded, his voice husky with need.

"Mmhm--ngh!" Casey nodded and, ever so carefully, leaned backwards and felt the wide tip of Raph's cock press against his slippery, waiting hole.

Leo bent forward, eyes fixated on the connection and movement happening just inches in front of him. The leaking, throbbing purple head of Raph's dick pulsed and smeared its juices against Casey's eager hole, and with a slight thrust, began to push inside. The skin pulled taut and Leo watched the muscles clench and unclench, his eyes wide as Raph suddenly thrust needily with a grunt.

The head of his dick slipped through the rim and his massive shaft slid eagerly in after it.

Casey cried out loudly, shaking the walls as he felt his body lit on fire with need. There was no pain, only a slight pressure, followed by a crushing wave of desire and pleasure unlike anything he'd ever felt before. It wasn't that his body was simply enjoying being fucked by his lover, it was that he was purpose made for this task.

He was built to be bred now.

Raph grunted with a similar realization, his shaft being squeezed in a heavenly vice on all sides. The way Casey felt around him was impossible to ignore, and he shouted out in unison with his lover, driving his body up and into the other turtle. He could feel his balls churning in their leathery sack, an orgasm quickly approaching.

Casey was made for this. This was what the mutation wanted most, and it craved being filled.

Being_bred_.

Leo watched this all and moaned lewdly, pumping his own dick with one fist and pinching the base of Casey's tail with the other. He'd leaned forward, his nose and mouth a hair's breadth away from the stretched hole and thrusting dick. Raph pounded away at Casey with slickness and ease. He couldn't help but sniff deeply and lash out his tongue, catching the tip on Raph's cock as it plunged past Casey's rim.

A sudden jolt of pleasure arced through Leo and he cried out, an orgasm ripping through him and shooting several blasts of thick cum upwards as he twitched and grunted. It had come out of nowhere, like he was a teenager again, unable to control his body. The thick seed shot upwards and landed down on top of Casey's shell and backside, coating his entrance.

Casey felt the warm, oleaginous seed splatter down on him and heard Leo's gasping cry of release and his body reacted automatically. His hole clenched down hard on Raphael's utterly massive shaft inside of him, driving both their pleasure beyond their limits. The air thickened with haze and Casey met Raph's thrusts with a deep bounce of his own, sending the throbbing dick inside him deeper as he spasmed with his own orgasm.

His dick had been bobbing in front of him, untouched and flaring outward uncontrollably as Raph fucked him. But now, it throbbed and jerked of its own accord, his balls jostling with force as he spewed thick turtle cum in heavy waves upwards and outwards. The first few shots splattered Raph's plastron with fresh seed but, as it continued, the shots seemed to grow in force and power and soon shot out further, landing on Raph's snout, the bed, and even the back wall.

Casey screamed with satisfaction and arched back, driving Raph's dick into his body. His lover came undone moments after, shouting with his release as he grabbed Casey's hips and ground them into his, filling his brother's virgin hole with his potent seed. His tongue licked out and caught some of the blasts of Casey's cum as they landed on him, letting the mixture sit on his tongue as he grunted heavily, still in the throes of his release.

Then automatically, he leaned forward into Casey's torrent of spunk and buried his snout in the other turtle's neck, biting down hard through the skin. Instinct had taken over and he thrusted up harder, biting for blood as he eyes glazed over and he lost himself to his mate.

Casey was stuck between a gasp and a shout at Raph's mating bite, the teeth digging into the curve of his neck and drawing blood in the most pleasurable way. Raph had claimed him, bred him, and now they were bound as mates. His instincts sang out as he let out a rumbling noise he'd never made before, one that was instantly matched with Raph's own, the two creating an odd sort of harmony together.

A churr.

He could feel his body filled with warmth and he shuddered as his orgasm began to taper off, each shot of his seed landing closer and closer until it stopped completely. But his body was still going, still sending those signals to his brain that he was being bred, being filled. Those same pleasure receptors fired away as Raph's thrusts slowed, the other turtle's cum leaking out past his rim and coating his taint and inner thighs.

Any thoughts were incoherent among the three of them. Their bodies were still filled with the haze and still on a hair trigger for any form of pleasure, but their minds were reeling from their releases and the nearly incomprehensible desires they'd felt. Casey and Raph churred together for another minute, the last vestiges of their orgasm fading away.

Slowly, Raph released Casey's shoulder, lapping lightly at the raw punctures he'd made and tasting his mate's blood on his tongue.

Leo slumped forward, softly colliding with Casey who leaned forward at the sudden weight of his brother. Raph somehow managed to reach up and steady the two of them, shifting slightly on the bed.

Casey felt Raph's dick pulse inside him again and he leaned forward, falling softly into Raph's side. He slid his legs over his brother's and maneuvered to press his snout against the other turtle's next to him. Raph's long shaft was still inside his hole, though more and more cum leaked out with each movement.

Following Casey's lead, Leo gracefully placed himself on Raph's other side, the larger turtle now holding both of them in his arms.

With a needy sigh, Casey pulled Raph in and kissed him deeply, smiling as he tasted his own seed for the first time. It tingled on his tongue, and he moaned at the flavor, somehow perfectly salty and almost sweet.

Leo's wandering hand found Casey's and their fingers intertwined, gripping strongly as they all collectively breathed a sigh of relief, and of contentment.

"We gotta do this again." Raph said first, breathing hard as he kissed Casey softly.

With a nod, Leo shifted himself up, placing his head on Raph's plastron and watching his brothers moan into one another as they kissed.

"Mmm--f-fuck!" Casey shuddered as Raph's cock finally shrunk enough to pull out of his very well used hole and a torrent of seed flowed heavily out of him. He glanced back at the mess of slickened sheets and cum-drenched pillows, shaking his head with a soft smile and closing his eyes as warmth flooded over the three of them.

"Sorry 'bout the bed, Leo."