Medusa ( Quirk Au BNHA )

Heat

"Don't fuck with me, you know what's up, the shit is up with you and that bastard?"

"...Kacchan, we're cousins, I don't know why he keeps on acting that way towards me but we're just cousins, you can ask my dad about it"

Katsuki blinks.

"Cousins?"

"Y-Yeah-"

"Are you fucking kidding me?!" Izuku yelps when Katsuki slams a hand to the wall next to him.

"You're telling me I got jealous of your fucking cousin?!"

"I-I'm sorry?! W-What do you want me to do?!" He whines, pressing up against the wall.

"Oh fuck you, I'll fucking mark you all up how about that" Katsuki growls, leaning his face close to the side of his neck.

"K-Kacchan! Y-You- there's not gonna be a-any mark there those a-are just my scales! Y-You can't mark them!"

"Do I look like I give a shit?!" Izuku cries out as Katsuki bites down on sensitive scales, his legs felt like jello, he almost collapses but Katsuki catches him, lifting him against the wall by his hips, Izuku instinctively wraps his legs around him, afraid to fall, that somehow egged on Katsuki as he bit harder.

"K-Kacchan- Kacchan, f-feels weird! G-Get off...!" Izuku weakly mewls, trying to claw Katsuki's back to get him to release him, for some reason, that also just motivates Katsuki more, roughly sucking on the sensitive area, if Izuku was a normal human he would've gotten a hickey but here he is, a flushed, moaning, trembling, drooling mess because Kacchan is sucking on his scales, what a nerd.

Katsuki pulls away to press on Izuku's mouth instead, he tried to pull away but Izuku pulled him back in, Katsuki's eyes widen when he felt something curl around his thigh, he glances down from where Izuku was kissing him and noticed how his tail, wrapped around his leg, slowly started to trail up, he presses on Izuku's shoulder before pulling away.

The greenette looks at him, his pupils blown wide, smelling weird as all hell and still drooling and flushed.

"Deku what the fuck?"

"...M-Mate...!" Izuku mewls trying to pull him closer, "P-Please!"

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It was kind of hard to get Izuku home when the greenette was practically pressing up against every part of him and I mean ever part of him, he just carried the greenette when he wouldn't stop groping him when he was down on the ground but now he's trying to kiss the blond each time Katsuki does so much as glance at him as he squirms in his hold.

"Auntie? Izuku's acting weird!" Katsuki said, entering the door, damn manners Izuku needs to get checked.

"Huh? What's up with my son?" Hisashi says, coming to them immediately. Katsuki puts down the greenette.

Hisashi's eyes widen.

"Izuku... smells like he's in heat"

"The fuck? Only female snakes smell when they're in a fucking heat"

"..."

"No way, you telling me Izuku doesn't have a dick-?!"

"No Izuku's a son damnit! Either way, thanks for bringing him home-"

"Alphaaaaaaa" Izuku mewls, pawing on his father.

"Izuku no! Daddy's not gonna do that to you!" Hisashi exclaims, lifting his son, Izuku chirps happily at having himself touched.

"Inko! We need to get him to a doctor quick!"

"..." Katsuki leaves the scene, trying to get the scene out of his mind.

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"You're telling me that my son is a girl-?!"

"Not exactly, Hisashi-san" The doctor sighs. Izuku is curled up prettily on his lap, looking like a cat,

"There's an opening to every snakes tail so we checked if Izuku has one and... he has one-"

"Does that mean he can-"

"No it's not functional, Izuku can't get pregnant or anything like that" Inko sighs in relief.

"But he still releases pheromones that will attract other male reptilians to him, Izuku hasn't had his heat yet am I right?" Inko nods.

"He's never acted like that before"

"It seems like there was a sudden trigger to his heat, most of the time rising temperature could play a part in a snakes heat cycle, after hibernation snakes start to go in heat but it's the middle of summer right now, it would make sense since UA is well ventilated when it's hot out but the problem is that today is currently the coldest day of summer yet, it would make much more sense if someone else was..."

"Either way, we noticed that there was very little space at the end and also that his tail is pointed at the end, his snake part seems to be a girl but he's a biological male, we have some heat suppressants we can give him and I suggest that he starts taking it for atleast 10 days to make sure that the heat won't come back and for him to carry some every day, heats would normally happen once or twice a year but most of the time, in quirk users with animal features, it goes with a trigger instead with the season, you should know this Hisashi-san" the man nods.

"We suggest telling someone in school, maybe a teacher about this just so that they can help if Izuku goes into heat, we don't know what triggered his heat or if it can trigger him again." The doctor said, he leaves for a couple of moments before handing them a bottle of heat-suppressant pills.

"Since it's his first time, we'll give this to you for free, once Izuku takes it he should be back to normal after a few hours, after that he needs to take it twice a day, preferably at breakfast and dinner, either way-"

"Mhmm, alpha?" Izuku asks, looking up to his father.

"No sweetie, go back to sleep, there's no alpha near, no alpha" Izuku pouts and goes back to sleep, Hisashi sighs.

"Even if I don't want to do anything I somehow feel like a dirty old man"

"That means Izuku's heat is affecting you, you have a reptile quirk after all- I suggest feeding him and letting him take the heat suppressant pills soon or you might be thrown in heat too and.." Hisashi looks horrified.

"Thank you for your help doc, sorry I'm gonna go feed Izuku now bye!" Hisashi says, running out with Izuku in his arms.

"..."

"..." Inko sighs.

"Why am I the only normal person in our family...? He left the pills with me, stupid Hisashi."