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Kutamo Lab Location #4 - Growth Studies

A multitude of male furs sat waiting in what looked to be the waiting room of a doctor's office. It had the same set up, a big coffee table with magazines, old and new, a TV hanging on the wall nearest the check in desk with a generic daytime game show running, and decently cushioned seats aligning the walls of the room. The males waiting in the room were either filling out a large packet of information on a clipboard or waiting for their turn to be finally seen.

Among the waiting was a blue furred monkey, average in height and muscle tone, and a brown horse who was nearly the opposite. The equine stood very tall, roughly nine feet, and was packed with muscle. This became even more evident once they stood up, having both heard their names called from a Badger in a lab coat. They each gave a glance to one another before moving to follow the badger out of the waiting room and into a hallway, the equine allowing the monkey to go ahead of him.

The badger scientist had little to say as they went, going down a myriad of hallways. Just how big was this place, and how did one keep track of where they were going? It was similar to how hospitals felt, not only confusing to traverse but very clean looking, though less signs on how to get around.

"Right into here, please." The badger stopped at a door marked '1H Gym', pulling it out and stepping aside for the two to step inside. The monkey and equine would find the fairly large room to indeed be a gym, though more like someone's basement gym at their home. There were various pieces of weight lifting and exercise gear and equipment, but only one of each.

"Hmm." The equine hummed in thought, stepping into the middle of the room and glancing around.

"Are we going to be working out?" The monkey asked, moving over to stand beside the horse.

"That is correct." The badger stepped inside, letting the door close behind him. He marked something down on his clipboard then motioned to a minifridge on the opposite side of the room beneath a large mirror spanning across the entire wall. "In the fridge are two protein shakes, already prepared and ready for consumption. The horse..." He trailed off, flipping through his papers. "Ajax, will have the blue bottled drink and...Yolk will have the red bottle." The two test subjects share a quick glance before making their way over, the equine standing aside as the monkey got both the drinks out of the fridge. It was one of the really mini fridges, barely big enough to hold the two drinks inside it. They each took a hold of their respective drinks, giving them a curious look. Is this what they were testing?

"Do we just-" The horse had begun to ask.

"You will drink the entire bottle, toss the bottles into the trashcan near the fridge, then proceed to work out for the next half hour. What you decide to use or what kind of exercises you wish to perform are entirely up to you. Once the time is up the sci- I will return for the next phase of the experiment." The badger looked up from his clipboard, having sounded like he was reading from a script. "Any questions?"

The monkey shrugged. "Seems pretty straightforward to me."

"Very good, I will be back in 30 minutes." The badger promptly turned and left the room, the two subjects not having learned the badger's name.

"That was odd." The monkey spoke, unscrewing his bottled drink and giving it a tentative sniff.

The horse nodded in agreement. "Yeah, maybe it's his first day or something?" The equine opened his drink and quickly drank it all down with no hesitation. The protein shake was thick and had a strong berry flavor, prominently blueberry and blackberry.

Upon seeing the horse's eagerness, the monkey drank down his drink as well. His was just as thick, but tasted of strawberry and banana. "Mmm, not bad. Strawberry and banana. What was yours?"

"Blueberry and...something else. Can't place it exactly, but it was good. Not the best protein shake I've ever had, but good." The horse screwed the cap back on before tossing it into the waste bin.

"I dunno, mine seemed a bit...chalky, like it wasn't mixed well enough or something. Not terrible, I guess."

"So, Yolk, huh? That's a cool name. Eggs are great when you're going for muscle gain, quick, easy and tasty." The horse grinned down to the monkey.

Yolk nodded, heading over to the stand of hand weights. "Yup, and your Ajax?" He decided on 20 pound weights after looking them over, taking one into each hand before putting them to use.

"That's me! Glad to meet ya. I guess we should get to work, eh?" He shot another smile to the monkey, heading over to the treadmill. "Good thing we dressed for the occasion, eh?" The equine motioned down to his T-shirt and shorts, the monkey dressed in a similar fashion.

"I figured an experiment about muscle gain would be vigorous. Only makes sense to dress the part." Yolk responded, arms curling and lifting the weights.

"Heh, I didn't even think about that! I just had plans on going to the gym after this, but maybe I won't have to depending on how well this goes." The equine got onto the treadmill after putting it as a moderate jogging speed.

Yolk eyed the jogging equine, the guy was huge, tall and muscled, and was quite friendly. "Why are you even here, though? You're already massive. I don't think any more muscle could fit on you."

Ajax chuckled, giving a quick glance to the monkey. "Gotta keep working out to keep the gains, bro! I'm also trying to increase my bench weight. I can only do about 300 right now, hoping to get to 325 in the next month or so!"

Yolk was surprised by that to say the least. The big guy was trying to get even bigger when he could already lift so much weight? Was he trying to be a bodybuilder or something? He shook his head, focusing on his own workout. Yolk went from hand weights to an indoor rower, and just when he was finishing that the door opened, the badger returned.

"Time for the next portion of the experiment." He explained, looking over his papers as he stood just inside of the room.

Ajax turned his machine off, having spent the whole 30 minutes jogging, with the last 10 minutes being a brisk run. He was dripping sweat and panting for breath, using a small towel from his pocket to wipe his face and muzzle. "Cool cool, what's next?"

Yolk was also sweaty, though not nearly as much as the horse was. He still couldn't believe the equine had jogged and ran for so long with no breaks.

"For the next part you must both undress completely." The badger said matter of fact, looking up from his paperwork.

"Sure thing!" The equine wasted no time in peeling off his shirt and tossing it aside, his shorts and boxers quickly following suit. Ajax had no issue standing nude before the two other males, his big sheath and heavy balls on display.

Yolk was a bit more hesitant, waiting till the horse was completely nude before following his example. He had to kick off his shoes and socks before he could pull off his shorts and boxers, his shirt being the last thing to be removed. Not only was he dwarfed in comparison to the horse in height and muscle, but his cock and balls were no match as well.

"Very good, now..." The badger looked to his papers once more, reaching into his pocket after some reading to pull out a small circular remote. A single button press and a seam appeared in the wall as a rectangular section of the wall the size of a door pushed out, sliding aside to reveal what appeared to be a closet sized room.

"Whoa, that was cool!" The horse exclaimed, a big smile on his face.

Yolk was impressed as well, but did little to show it besides staring at the newly revealed room.

"Ajax, you are to enter the changing room first." The badger looked to the equine, waiting for him to proceed.

"Sure thing, Mr. badger!" He gave the scientist a smile then proceeded to the closet, the walls and flooring were the same as they had been in the 'gym', white and sterile. There was nothing of interest in the room, not even a light source which became very apparent when the door slid close, the horse in darkness.

The badger waited patiently, everything remaining quiet except for the soft hum coming from the wall. The horse had only been in the wall for less than a minute before it opened once more, the equine turning and stepping out. The horse was still nude, but now he sported a leather strapped harness, not unlike a climbing harness. The straps went around his chest, waist, and groin.

"This is pretty cool." Ajax said while admiring and testing the straps, not sure where they connected. It almost seemed like it was seamless with no buckles or way to remove it.

"Yolk, it is now your turn to process into the changing room." The badger's gaze was now on the monkey.

"Uh, right." Yolk glanced to the equine, looking over the horse's figure which seemed to be sexier with the leather harness. He proceeded into the 'changing room', the door closing promptly behind him and everything going dark. Nothing happened at first besides the low hum of hidden machinery in the walls coming to life.

"This is-" The monkey jumped when he suddenly felt leather straps being pressed against his body. Some unknown force was wrapping the leather straps onto his body just like it had done for the horse. Yolk's nose twitched, a sweet scent suddenly overpowering his senses. By the time light began pouring into the room, he would find himself sporting a full blown erection and dressed just like the horse.

"Looks like someone enjoyed the new changing room." The horse chuckled as he watched the monkey leave the room, the wall closing up behind him.

"Well, yeah. Leather is pretty sexy." Yolk waved off the horse's comment, playing it off as if this was completely normal. Of course it was not. What had happened to make him so incredibly erect, his human styled dick standing tall and throbbing for attention? It had to have been that lovely sweet scent.

"Now that you are both changed, you must get into position." The badger paused, flipping through his pages for a diagram. "Ajax must stand in front, and Yolk must stand behind him, only a few inches apart.

The two test subjects looked to the badger and then at each other.

"Whatever you say!" Ajax was unphased by the situation, probably because he wouldn't be facing a big bubbly ass.

Yolk hesitated a moment before stepping up behind the horse, his head eye level with the horse's lower back. He only had to tilt his head downwards slightly to get an eyeful of the equine's toned but thick ass cheeks. He wasn't sure if it was more embarrassing to already be fully erect behind the equine, or if he only got erect once in this position.

"Very good." The small remote was pulled out once more and a button pressed. Within the blink of an eye, the metal discs that connected the straps together popped out, the top half of Yolk's discs connecting to Ajax's sunken discs, easily snapping into place. The two were now connected by small but strong black rope.

"Whoa! What the hell was that?" Yolk jumped from the sudden black blurs, looking from himself to the horse.

"Did something happen?" Ajax asked, turning his head to try and look behind himself.

"Just keep still." The badger calmly spoke, pressing another button. Yolk's harness began to 'reel in', except he was hooked to a much bigger fish. This led to him being pulled right against the horse's ass. It didn't stop there, it kept going. The monkey being pulled up, sliding up onto the horse's back.

"Gah!" Yolk exclaimed, his dick twitching as it slid between the horse's ass cheeks. Even once he was basically strapped to the horse's back, it tightened some more, causing his dick to prod at the horse's puffy hole.

"Whoa there! We haven't even gone on a date!" Ajax chuckled, barely phased by the monkey's weight on his back or by the cock poking at his tail hole.

"Now that you two are connected, you are free to do as you like without leaving the room or tampering with your outfits. "I'll be back in...." The badger read off from his papers, completely ignoring the strange situation the two subjects found themselves in. 'Hmm...Doesn't say." He looked up to the horse and monkey. "It shouldn't be more than an hour or two!" With that said he turned and left the room.

"Definitely seems like his first day." Ajax commented once the badger left.

Meanwhile Yolk was squirming around, feeling bad for basically being mounted to the horse. "Hey, uh...Sorry about this! This is really weird. What does this have to do with muscle gain, anyway?"

Ajax looked back over his shoulder to the monkey. "Beats me. Don't worry about it though. I'm gay and..." He gave a coy smile to the monkey. "Well, you're pretty handsome. Could be worse, eh?" He chuckled.

Yolk calmed down a bit after hearing that. "You're a real looker too. I'm sure you knew that."

The equine smiled before turning his head back around. "I get that a lot. Still nice to hear it though." His gaze shifted to the treadmill. "Guess I'll work out while we wait for whatever is supposed to happen. It's my leg day, and I still need to run or jog five more miles."

"You're going to exercise with me strapped to your...back?"

"Why not? It'll help with my endurance!" Ajax replied cheerfully, stepping over to the treadmill and getting it set up before stepping on. He went at a light jogging pace to get warmed back up.

"Oh-okay" The monkey replied, his cock continuing to throb. How could it not as he bounced around on the horse's back, cock sliding around between those cheeks. Even wrapped his arms around the horse's torso did little to keep himself steady.

It wasn't but a few minutes until the equine's stride had a hiccup in it, quickly recovering and continuing to jog. "Mmph...Is my backpack getting excited?" Ajax chuckled, his sheath starting to swell.

Yolk's dick was slipping into the horse's back door, aided by the precum leaking from his tip. He hadn't meant to penetrate the horse, but damn did it feel good. "Your backpack is just enjoying the ride."

"Heh, no complaints here."

It didn't stop there, the monkey's cock kept throbbing, leaking and sinking in further. Yolk didn't realize it at first, not until he was a good 5 inches into that ass. How was that possible? His modest size had barely poked at the horse's hole, given how he didn't have those ass cheeks spread apart for proper penetration.

"Nnngh...Damn dude, are you still getting hard?" The horse questioned, that dick in his ass was getting bigger. He could've sworn the monkey had already been fully erect, and it hadn't looked that big.

"This is gonna sound weird, but..." Yolk huffed, resisting the urge to start thrusting into that lovely ass. "I was fully hard after I left that weird room. I think...my dick is growing." Even saying it outloud didn't help it sound any more plausible, but he could quite literally feel himself slipping further and further into that ass.

"Shit, that's kind of hot." Ajax adjusted the speed, slowing down to a brisk walk. "I thought this was about muscle gain though?"

Yolk loosened his grip on the horse's torso to pull back and look down at himself. He had felt a heat building up in his arms and legs, but only now did he see what it meant. The monkey's muscle groups were slowly inflating, his muscles getting bigger. "Uuuh...Seems like I'm getting more muscle."

"That kind of stinks....Oh well, you could use it more than me, heh." Ajax was a bit hurt he wasn't gaining any muscle, but it was alright. His little friend would just look sexier is all. "Can't say I've ever exercised with a dick in my ass before."

"I've never fucked a guy while being worn as a backpack. First time for everything I suppose." Yolk began to huff and puff despite being the one not working out. His cock kept throbbing and growing, his arousal only getting stronger while his dick gained not only length but girth.

The horse's backside was being stretched open. An average sized cock was nothing for his big posterior, but that same cock was now getting thicker than a soda can and still pushing further into him. "Mmmph.." He lowered a hand to his stomach where a bulge was forming. He didn't seem to have any issues or pain, evident from his equine length growing free of his sheath. "Your big dick must be a side effect. A different 'muscle' growing....But damn, I don't mind at all."

Yolk groaned in agreement. He took hold of the horse's sides with his hands and thighs with his feet, beginning to thrust back and forth into that accommodating ass. His thrusts only had a few inches of slack given to him by the harness. The monkey's balls were growing in size as well, going from cherry sized to baseball sized, and still swelling.

Ajax stepped off the treadmill when that bulge only got bigger. Not only pressing out further but sliding up, the bulge growing up his torso. "Oh fuck...That's really fucking big." He grunted out, moving over to the mirrored wall to brace himself.

Yolk was too enraptured to even speak, the horse soon unable to speak for a different reason. He wasn't able to tell the extremes his cock was growing to until he peered around the horse's back, able to see the reflection of his cock bulge growing up right into the horse's throat. "O-Oh, fuck! Shit!" He was brought out of his sex clouded mind, worried for the horse's health as that bulge went up into the horse's throat.

Ajax didn't seem to be as alarmed. His eyes had gotten wide in shock, unable to speak as his throat was filled. After a few moments his hand lifted away from the wall to give a thumbs up. He was still able to breathe just fine, even with a cock as thick as a two liter soda bottle in his throat. The equine had to tilt his head back, looking straight up to the ceiling as that cock pushed out from his throat and into his muzzle.

Yolk had calmed down a bit, enough to get back into thrusting. His cock twitched and spurted precum, big ropes of it shooting out of the horse's mouth thanks to his melon sized nuts. His cock seemed to have stopped growing now, once it was resting behind the horse's teeth. "Fuck dude...I'm gonna cum."

Ajax would have nodded, having to settle for another thumbs up. He was loving it just as much as the monkey, his own cock fully erect and dribbling pre. It was a big rush when he felt the giant cock inside him, using him like a fleshlight, begin to shoot cum. He was able to feel it rush up from his ass to his mouth, splattering onto the mirror.

Only the first few shots flew out of the horse's mouth. The monkey's body and harness had relaxed when he had begun cumming, meaning he slowly fell down to the floor, his cock sinking down. It kept spurting, his cock head settling in the horse's belly where the majority of his cum would build up. Once sitting on the ground, looking up to the big ass stretched around his even bigger dick did Yolk get a proper sight of how big his dick had gotten.

Ajax coughed and sputtered, able to breath normally once more, a hand going down to his bulging stomach. "Damn, bro. That was intense!"