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Izuku was willing to do a concerning amount of things in the name of science. He couldn’t help it. Discovering new things and figuring out how it worked was part of what made life so fascinating. All his life Izuku strived to learn more and more. But fucking essentially what was a tentacle monster was… pushing it. If only a little bit.
Lonkero’s were exclusively difficult creatures to even see. So little information of them existed due to their reclusive nature. For the longest time they were considered just a myth until they found one mummified in a bog. Their humanoid structures left skeletons unclear. Disformed human/monkey, or a creature that almost doesn’t exist?
When Izuku’s team actually caught one and brought him back, Izuku had been beyond ecstatic. Seeing one, presumably young and in his prime, was such an amazing discovery. They named him Katsuki to keep things simple, and further went to called him Kacchan. The cutesy nickname didn’t match up with the creature very well. He was furious to have been caught and let them know he was mad every step of the way.
God was he beautiful, though. Bright red eyes, orange skin and rounded spikes protruding on his shoulders and along his spine. The splattered black marking over his eyes was akin to a mask. He had a multitude of tentacles that appeared to be able to appear pretty much anywhere on his body, varying in thickness and number, but he was stubborn. When they came in to inspect him, he’d withdraw everything.
There was a little problem with him trying to kill all the researchers, but a powerful shock collar that monitored too much movement kept him in line. Kacchan would growl menacingly, but quickly learned it was easier to be poked at for a bit rather than make a scene.
The only person he was ever good for was Izuku. They weren’t exactly sure why, but Izuku suspected it was because he treated Katsuki a bit more like a nervous child at a doctor’s visit rather than an animal. He always used a soft voice, let him be aware of what he was doing. Kacchan relaxed better if he knew what was going on. That left him being likely more on the human intelligence scale rather than that of an animal, but there was no way to prove that at the moment.
They actually didn’t know for certain that Kacchan was male, but sexing him didn’t appear to be easy. Much as they figured out was that he was a bit like a reptile, genitalia being internal and hidden behind a slit by his crotch. However, they couldn’t exactly force that open and stimulation so far was proving fruitless.
Then they asked Izuku to be the one to try and get a reaction out of the Lonkero, leaving him bright red. It wasn’t just sexing, but samples of cum or a slick would help move research along. Also maybe they could figure out a thing or two about mating habits. So, not only were they asking Izuku to get Kacchan all hot and bothered, they wanted him to get off the creature.
After ample pressuring and under the terms that it wasn’t recorded and no one else was present, Izuku caved. It was just for his job, right?
Once everyone had gone home, Izuku slipped into Kacchan’s cell. He craned his head up, clearly aggravated after being strapped down for so long on the examination table. Usually by now they’d let him off, and he’d go sleep in the corner of his makeshift bed. They had given a proper mattress and blankets, but the grumpy Lonkero had torn it to absolute shreds and rearranged everything in the corner.
“Hey, Kacchan,” Izuku greeted, more than a little nervous. The shock collar would keep the creature in line, but honestly it would be insanely easy to kill him right then.
Intense red eyes stared him down as Izuku stood at the side of the table. Swallowing hard, he ran his hand down down Kacchan’s stomach. Although the skin was soft, it more akin to leather rather than human skin. He growled in warning, but it was a softer sound, nothing like the vicious snarls the other researcher’s normally got.
Izuku’s hand traced further down, thumb edging around the slit. The growl Kacchan was making turned into more of a curious trill, head craning to see what Izuku was doing. Using both hands, Izuku continued to thumb at the slit, making the Lonkero squirm under his touch. After a few minutes of alternating touches and strokes, Izuku nearly gave up until the slit parted just a bit. It was hard to tell, but it looked like the head of something, be it a cock or clit, was poking out. Just barely, but it was there.
Trills turned into chirups as Izuku ran his thumb into the seam, the inside slick. However, it didn’t seem like he was getting anymore of a reaction. Maybe Kacchan was actually female? Izuku wasn’t confident enough to entertain the thought of trying to stick his fingers into the creature.
After a moment of debate, Izuku leaned over and licked. He moved his hands to Kacchan’s hips to keep him from bucking up as Izuku lapped over his entrance. Izuku’s cheeks were burning, wondering what the hell he was doing. Finally, more of that head popped out.
That’s definitely a dick, Izuku thought, focusing his attention there. Much more quickly, it slid out completely, wiggling to get further into Izuku’s mouth. Pulling back completely, Izuku needed a moment to comprehend what he was looking at. The only way Izuku could classify it was a tentacle dick, being solid yet able to bed and curve seemingly at the creature’s will. Izuku stroked it, watching in amazement as it tried to curl around his hand.
The shameful next thought was, I want that inside me.
It was so slick and smooth to the touch. Even being thicker and longer than the average male, it would probably fit inside Izuku. Not as thick as getting double penetrated, that was for sure, but god damn.
Izuku had restraint though, and mostly used his hands to stroke over the thick length, mouthing messily at it’s head. He made mental notes that he was going to have to write this down later and give a proper explanation on how it worked. It took him a second to realize that he had tentacles winding up his waist. They were soft and exploring, not alarming Izuku to any danger. Honestly, he was surprised Kacchan was finally showing them.
They slid under his shirt and dipped below his pants. Part of Izuku wondered if maybe he should stop Kacchan, but ultimately did nothing. He was willing to admit he was hard the moment Kacchan’s dick fully slipped out.
It was dangerous to let the lonkero get such a good hold of him, but the glide of the tentacles on his inner thighs left Izuku shuddering with want. They were more like the rubbery texture of Kacchan’s dick, curling around anything they could. When they trailed under Izuku’s boxers and finally slid against Izuku’s dick, he moaned around the length in his mouth. The tendrils paused for a moment, teasing until it seemed that Kacchan was sure that it felt good for Izuku. Almost instantly the tentacles got wet, sliding slick over Izuku’s dick.
Even amidst the dirty situation Izuku had gotten himself in, he couldn’t help but wonder what was the biological purpose of the tentacles. Kacchan had used them for defensive purposes until they tried inspecting them, so it definitely wasn’t a mating thing. At first Izuku had assumed it was for capturing and holding prey, but being able to become slick was a weird trait to have in that case.
Izuku’s thoughts were abruptly cut off as a tentacle experimentally curled around his balls. The touch thankfully remained gentle and continued to explore further back. To his absolute disappointment, the tendril only slid up his crack, never pressing against his entrance. It drove Izuku wild anyways, whining loudly. The pressure and squeezing around his cock felt nice, but it wasn’t the nice firm pressure he was used to. To be fair, if Kacchan’s ever mated with another male, it would’ve been with another lonkero with a tentacle dick. He probably didn’t know how to pleasure Izuku’s stiff length.
After several minutes, Izuku’s hands and mouth were starting to ache. Kacchan just wasn’t coming. It was clear Izuku was heading in the right direction, but even the lonkero seemed to be getting as sexually frustrated as Izuku was. Maybe they should try something different.
To absolutely fulfill his earlier urge, Izuku pulled away and stretched, back sore from leaning over the examination table. Kacchan kept a firm grip on Izuku, growling at a hint of Izuku trying to get away. After a moment of debate, Izuku pulled off his shirt. His pants and underwear got caught around the tentacles that Kacchan had wrapped up to his chest, but he seemed to get the message, readjusting his hold to let the clothes fall to the floor.
Clambering onto the examination table, Izuku moved as much as he could with the tentacles trying their best to cover him. Once on his knees, Izuku made sure Kacchan was watching as he pulled a tentacle off his leg and moved it towards his entrance. With his free hand, he spread his ass cheek and rubbed the tentacle against his entrance until Kacchan got the hint. The slick tendril slid in slowly with ease. It was bigger than a finger, but not painfully so. Now Izuku could only sit there and let the creature explore.
With every inch the tendril sank in, Izuku eagerly waited for it to hit his prostate. It stroked and rubbed against his walls in the best of ways, something a toy could never accomplish. Izuku wanted about three more of them shoved inside until he was stuffed full and left drooling. A second one was already teasing at his entrance. He hoped Kacchan decide to slide that one in too.
In the meantime, Izuku started fisting his own dick, aching for more stimulation. After only a moment of watching, Kacchan, took over, a tentacle thicker than the others coming in to curl around his dick and pump. When Izuku keened, he swore the lonkero smirked, looking rather pleased with himself.
The second tendril slipped inside moments before the first one found his prostate. Izuku moaned loudly, and suddenly both tentacles were eagerly rubbing that spot until he came hard. Panting harshly, he looked down at the mess of cum coating the tentacle wrapped around his dick. Kacchan only stopped for a brief moment before continuing his ministrations, more enthusiastic than the first time.
After a third tentacle was pushed inside him, Izuku was ready to come again. However, given that Kacchan appeared to have very good stamina, Izuku didn’t want to get wiped out before he managed to get Kacchan’s dick in his ass. Reaching back, he gently tried to pull the tendrils out of him. Thankfully, they slid out. Crawling forward, Izuku hands pressed into Kacchan’s chest as he positioned himself over the creature’s dick.
Kacchan certainly knew where this was going, dick rubbing against Izuku’s ass, straining to get inside him. Carefully, Izuku lowered himself low enough to allow the creature to do so. Even with just the tip inside him, he knew how good he was about to be stretched. He sank down completely, his voice more of a scream rather than a moan as the dick writhed inside him all the way down.
It was hard to gain his bearings when Kacchan wasn’t patient enough to give him a moment. His cock rubbed and squirmed inside him, movement much more restrained than the earlier tendrils due to size. Riding a cock that could move on it’s own certainly was never an experience Izuku ever thought he’d have, but here he was. He loved every second of it. Every rise of his hips, Kacchan’s dick curled only to straighten out and thrust deep when Izuku dropped back down.
This also meant Izuku blew another load thirty seconds in. Despite the overstimuation, Izuku didn’t stop, stubborn and determined to get Kacchan off at least once. Eventually, though, his thighs got shaky and tired from bouncing. His body in general was rapidly losing energy to continue.
All the cries and growls from Kacchan let Izuku know he wasn’t satisfying him. Against his better judgement, Izuku came to a halt, pulled off, and turned around.
“Security,” he called out, waiting for a pling! of acknowledgement. “Turn off shock collar for the next two hours.”
“Turning off shock collar for two hours,” the voice repeated back.
Izuku didn’t think he could last two hours, but was playing on the safe side.
“Security, unlock restraints.”
“Unlocking restraints.”
This was probably the dumbest idea Izuku ever had, but figured the lonkero would be more on the horny side rather than the homicidal.
It took only a few seconds until Kacchan was on him big arms pulling Izuku against his chest. With a small yelp, Izuku was carried off the table over to Kacchan’s makeshift bed. The moment the lonkero sat down, Izuku was pushed down onto his cock. His mouth opened in a soundless moan, head falling back against Kacchan’s shoulder.
Thick tentacles wrapped around Izuku’s legs, holding them wide. Izuku felt tiny being held against Kacchan’s chest, and quickly becoming nothing more than a toy as the lonkero bounced him on his cock. The pace was a lot more brutal than Izuku’s earlier riding, filling the room with the sounds of Izuku’s broken moans. He was pretty sure he was drooling at this point. He’s always had a little bit of a thing for being fucked and used, and holy shit this was a dream come true.
Kacchan’s arms tightened around Izuku’s stomach, and he could feel the difference, feel how deeply he was getting fucked. It was definitely done purposefully, Kacchan letting out a pleased rumbly purr as he thrusted up into Izuku with more vigor.
After a while there was a tug at Izuku’s entrance that he wasn’t sure what to make of. It was hard to really focus on anything when he was being so vigorously bounced. Then the realization came in, making Izuku’s mind go blank for a second. He has a knot.
It wasn’t until Izuku came a third, then a fourth time that night did that knot finally slam home for the last time. It hurt, bigger than what Izuku was prepared for. But fuck did it still feel good anyways, especially with Kacchan’s dick still wildly thrashing inside him. Kacchan’s teeth sank into the crook of Izuku’s neck when he came, cock still squirming until it finally spent it’s load. The hot feel of cum so deeply inside of him probably would've made Izuku come again if he weren't so worn out already.
Kacchan released his hold on Izuku’s neck, licking at the mark and purring almost affectionately. His hands rubbed over Izuku's stomaching. Unlike a regular cock, Kacchan's dick didn't go soft, remaining firm inside of him. Dirty thoughts of letting himself become Kacchan's toy passed through his mind, but Izuku knew he wouldn't. But maybe he'd pay a few more late night visits to Kacchan if the creature was still eager to fuck him later on. Izuku had zero energy left and felt barely conscious after getting fucked up that good. Sex was probably ruined for him forever.
The tentacles that were keeping Izuku's legs spread finally released their hold. Laying down, Kacchan curled around Izuku, making sure he stayed firmly inside the little human. Izuku would have to get up before the others came in tomorrow, clean himself up (oh god, did he have to get the cum samples out of his own ass?), and write a report. Hopefully the wouldn’t ask about the lack of detail. There was no way a single word of this was ever getting anywhere.