Chapter Text
Sometimes Shouto dreams about waking up to Katsuki’s cock inside of him, and whenever he does he lets a deep rooted growl pour out of his chest. His body waits for Katsuki’s knot, flicks ears that are no longer there, and whines miserably when Katsuki cums inside of him and doesn’t lock them together. When he wakes up, he’s miserable.
The same thing will happen if he’s tired and any of his other boyfriends fuck him in his dreams, but it’s never as strong as it is in those early morning ones with Katsuki.
Shouto misses his tails, misses his ears, misses the hot stretch of Katsuki’s knot locked inside of him for hours at a time.
But he has other things to worry about. There are people to save, cities to defend, and paperwork to fill out.
So when the one year anniversary of the quirk accident arrives, Shouto can say he’s sufficiently distracted enough not to notice anything different at first. When he wakes up in the middle of the night and stumbles into the bathroom, he almost doesn’t think to look in the mirror.
But it’s as he’s washing his hands that he glances up in the dark.
Two toned ears flick back at him and he yips in shock.
“Shou?” Izuku calls out to him around a yawn.
“Holy fuck!” Katsuki shouts, and there’s a frenzied scramble in the bedroom. Shouto throws the door open to stare at Katsuki, Izuku, and Eijiro, all three of them transformed into those familiar hybrid figures. Katsuki has his pointed ears and fluffy tail, Izuku with those long floppy ears and furry chest, and Eijiro’s wings have burst through the back of his nightshirt while his leather tail thumps the bed pitifully. He’s whining as he tries to take it off.
He really liked that shirt.
“Why the fuck are you a rabbit again?” Katsuki asks, pointing accusingly at Izuku.
“Why are you a wolf?” Izuku shouts, whole body trembling. “Oh god, oh no, we have to be at a Hero Seminar tomorrow! What if this is another heat quirk?” He tugs at both his ears.
Eijiro finally gets his shirt off and pouts, tossing it to the floor before he looks up at Shouto. His tail swishes on the bed behind him and he holds out both his clawed hands. Shouto hurries over to him and climbs onto the bed, his tails swishing heavily behind him.
He feels whole.
While Izuku and Katsuki are over there having some kind of a crisis, Shouto climbs onto Eijiro’s lap and reaches down to stroke his cock. Heat quirk or not, he doesn’t care. There’s always been a primal urge to mate when he’s like this, and Eijiro’s cock is very obviously the most willing.
When he sinks down onto Eijiro, still full of Izuku’s cum from last night, he keens and rests his forehead on his boyfriend’s shoulder. He can feel Katsuki’s growl before he hears it, and then there are two men at his back. Izuku is kissing along his neck while Katsuki nips at the mark on Shouto’s throat.
They’re not going to make it to that Seminar. Shouto’s going to ride Eijiro until he cums, then if he has the energy he’s going to have Katsuki fuck him over the side of the bed while Eijiro works on wearing Izuku’s hyperactive sex drive down. Shouto’s fantasized about this moment for an entire year, he knows exactly how things are going to play out.
“Cum in me,” Shouto begs, already panting when Eijiro hasn’t even thrust into him yet. “Fill me up, mark me, mate me.” His tails thrash and Katsuki reaches down to tug at them with a heated growl.
He doesn’t know what’s going on, but god… it’s going to feel so good.
_*_*_
Twelve hours later and while the four of them are utterly exhausted, they’re back to normal.
“It’s apparently a yearly thing,” their doctor says as she stands from her chair. She’s used to at-home visits by now. “The hybrid genetics from your previous quirk accident seemed to have latched onto your DNA, and because of how… vigilant you were in your previous… mating,” it sounds like she’s trying to hold back a laugh, “it settled in to be reccurring. I have no idea how long or how many years you have left of this, but I suggest you keep this day free for the next few. I can do more research to try and figure this out though.”
Shouto nods, going to reach for his tails for comfort and pouting when he remembers they aren’t there.
They hadn’t fucked the entire time this go round, but they’d still tired themselves out. In fact, at one point Katsuki and Shouto had left the house simply to chase one another in the woods behind their house.
Sure, they’d fucked after, but they’d spent an hour just basking in the early dawn light before that. Chasing the scent of a river and pouncing on autumn leaves.
And… maybe it’s silly, but Shouto’s looking forward to this as part of his new routine. He already misses his tails and his ears, but now he knows that they’re a part of him.
He can’t wait for next year.