Work Text:
CWs and tags: teacher/student relationship, underage (mid-late teens) Izuku, a/b/o setting, alpha Izuku/omega Katsuki, Katsuki w/ pussy
Katsuki does his best to ignore the dramatic antics of his students, but when they're directing their energy, curiosities, and problems towards him, it becomes overwhelming. He eventually has to answer their questions, even if there are so many he could drown in a vat of their requests.
"Sensei, will you look at this?"
"I need your advice on this homework assignment."
"Will you help me with this problem?"
"What are you doing this weekend, sensei?"
The last one catches him off guard. He looks up from where he's gathering his things, and then looks up even more. Stupidly tall teenaged alphas make his neck hurt.
"What do you want, Midoriya?"
A sheepish blush crosses his face and he stutters slightly, but he doesn't move. He even leans in closer, resting a hand on Katsuki's desk. Why does his hand take up so much damn space?
"I- I asked what your plans are for the weekend?"
"I heard you." Katsuki fights against the temptation to roll his eyes at one of his students. "Why would you ask about my personal life?"
That rosy color spreads farther on Midoriya's face, making his freckles stand out more than usual, clearly embarrassed but he doesn't move his hand or step away.
"You seemed agitated today, so I hope you have time to relax over the weekend."
Katsuki narrows his eyes. The response doesn't answer his question, but he avoids pushing for an explanation. He never bothers pushing for answers with his students when they're not ready to answer.
"I'm fine," he grumbles out. "Go on then. You know classes are done for the day."
He lingers like he wants to say something else but hesitates. His eyes catch on Katsuki's fingers tapping a meaningless rhythm against his thigh.
"Something else on your mind?"
A sigh escapes Katsuki's lips before he can restrain himself. But it does the trick. Midoriya stands up straight, looking even taller. Steadying himself, maybe shaking off nerves. Careful breathing and a moment with eyes squeezed shut lead up to Midoriya finally speaking.
"I still don't understand when to use each of these formulas. Will you help me?"
Thoughts of home, last night's leftovers, and his cozy nest fly through Katsuki's head, but he puts them aside. That will have to wait, it seems. He drops his heavy bag.
"Fine. Sit down."
"Right now?" Midoriya's voice goes high pitched. "Don't you want to go home to your alpha or something like that? Not that you have to tell me what your plans are, it just seems like you're—"
"Midoriya. Take a seat."
He scrambles to sit at the nearest desk, looking up at Katsuki with bright eyes. The eagerness is almost adorable.
"Where are your notes?"
The kid has the gall to look sheepish. The notebook he pulls out opens to a blank page.
"Before you yell at me," Midoriya starts, already defensive. "I broke my hand so I couldn't take my own notes, and then my mom got really sick so I was taking care of her, and I can't really keep up with everything. I'm really sor—"
He stops rambling mid-sentence when Katsuki holds up a hand. Good. At least he can listen.
"Stop. I don't need the minute-by-minute breakdown or the apology. I just need to know where to start."
He pulls up a chair next to the desk and starts paging through the notebook without a word.
"Please don't look, it's embarrassing."
"How much do you feel like you understand?" Katsuki asks as he flips through the notebook, ignoring the plea.
Hands flutter in the air around the desk but Midoriya doesn't actually snatch it away. Both of them freeze suddenly, however, when Katsuki stumbles across a sketch taking up an entire page. And it's not just doodles of classmates' names or mindless patterns; it's a full page drawing of Katsuki's face.
Honestly, he's a good artist. The shading seems real and the linework is steady. At least by the very limited knowledge Katsuki has, it really is nicely done.
"I'm so sorry, I know it's weird, but you looked so pretty that day, I couldn't help it."
"You got my nose wrong," Katsuki mumbles, grasping for something to say.
He's quiet at first, likely trying to will away the heat of splotchy blush on his cheeks. There's no response, and when Katsuki glances his way, he's staring at his hands. When he does speak, it's too mumble something under his breath.
"Speak up."
Finally lifting his head, Midoriya's face is red enough that Katsuki feels almost guilty about embarrassing him.
"I- I said I know I got your nose right because I stare at it all the time."
The words linger in the air. Katsuki blinks hard for several seconds, his mind completely blank before he continues flipping through the notebook. The distraction and return to familiar territory is desperately needed. But before he can turn the page more than a couple times, the notes are abruptly pulled out of his hands — but not before he catches a glimpse of another page filled with smaller drawings that look remarkably like Katsuki.
"You're good at that." He offers the praise like a peace offering.
"Thanks," Midoriya mumbles, still bright red in the face. "Can we, umm, start on Monday instead?"
The hesitation in his voice is obvious, but he does make eye contact as he asks. Katsuki's proud of himself for only slightly pursing his lips before nodding.
"Try to clean up your notes or come back with specific questions. That way we'll be able to see where we need to start."
Relief overtakes Midoriya's countenance, but there's no undoing the pretty pink on his freckled cheeks.
"Thank you, I'll see you next week!"
He scurries away as fast as he can. In his hurry, he drops something at least three times before he finally manages to run out of the room. Shaking his head, Katsuki returns to gathering his own things. Crossing the length of the room and reaching out to turn off the lights, he sees a notebook, under a desk just far enough to be missed by a student rushing to leave.
He picks it up and his focus settles almost instantly on the name scrawled on the front of it. Of course it belongs to Midoriya. There's no good reason to do anything but set it on the kid's desk and leave it there for him to find next week.
Yet Katsuki sits down in front of it. It doesn't fall open on its own, but he gently opens it himself. He's surprised to find page after page of drawings — most depict still life, plants, animals, and sometimes a woman who looks remarkably like Midoriya, with the same curly hair and sprinkle of freckles. Possibly his mother.
But once every few pages, Katsuki sees himself. It should feel disconcerting. Unnerving or creepy, really. But all Katsuki feels is like an intruder. Like he's invading Midoriya's privacy. The pictures of himself seem to reveal more about Midoriya than himself. Or maybe he just sees something curious and wants to understand his student a little better.
Whispering voices from the hallway suddenly become strikingly audible. He slams the sketchbook shut and leaves it behind. Perhaps something in the air makes his thoughts spin out of control and instill the need to run. First it was Midoriya, and now himself. Whatever it is, it doesn't matter, not when he shuts it all out of his mind and focuses on the list of groceries he needs to pick up.
-----
By Monday, he forgets his promise. At least up until the moment Midoriya walks by him at lunchtime. He smiles and gives an awkward little wave as he dashes out of the room, but Katsuki stares after him, only for a moment. He remembers now, and he won't have to embarrass either of them by forgetting at the end of the day. But then the abandoned sketchbook comes to mind again, and he stares at its unusual presence on the edge of his desk. He feels like he's still staring at it absently, hours later, when Midoriya hovers awkwardly in front of him.
"Today still works, right?" There's a slight waver in Midoriya's voice. "You don't need to leave right away? Go home to someone?"
Katsuki nods and waves him off, intentionally not responding to the probing question. The kid doesn't move. Instead he fidgets, twisting his grip around the strap of his bag so tightly that it might tear under the strain.
"A nod is a yes, Midoriya," Katsuki says through gritted teeth. The headache that's been creeping up on him all afternoon throbs painfully.
"Okay!" The tension doesn't lessen — if anything, it goes impossibly more taut even as he responds affirmatively. "I have lots of questions this time, so I'm ready, I promise."
He might as well be a flash of lightning considering how fast he moves to take a seat. Taking a deep breath, Katsuki moves to sit beside him. The sketchbook can wait so there isn't another distraction like the last attempt at a catchup lesson.
Midoriya pulls out a long list of questions and immediately begins rattling them off all at once. They blur together for too long, hard to comprehend due to the sheer speed at which he reads, before Katsuki realizes something significant.
"These are questions about next month's material."
A small, awkward laugh fills the air, but he looks up at Katsuki.
"I read ahead when I'm nervous, and this class is completely nerve-racking for me. But I still need your help!"
For a brief moment, Katsuki watches him, waiting to see if he's being serious. There's no wavering, just uncomfortable shuffling under Katsuki's observation. Without a word, he goes back to his desk for a stack of papers before settling back down. It doesn't take long for him to find the packet he needs.
"Try to answer this," Katsuki demands. Before the kid can hesitate for long, he shoves a sheet of paper into his hands. "Not graded. Just do the best you can, and don't force yourself to write an answer if you don't think you understand."
Midoriya immediately starts working on it, tucking the paper close and bowing his head. It's endearing. He chews his lip the whole time, but he barely pauses to read each question's instructions. Katsuki doesn't look away from him even once, fascinated by his determination. When Midoriya shoves the paper into his hand, he scans over it as quickly and thoroughly as possible. He lets it fall out of his hands as he squints at his student.
"This is a test for two weeks from today. You don't need my help with this."
Panic springs to life in Midoriya's eyes.
"No no no, I don't feel comfortable about this section at all!" He clutches at his pencil like it's a lifeline. "Even if I know the answers I don't feel prepared and I missed so much that I'm worried I'll feel unprepared for the rest of the term, even if my answers are right."
It's impossible to contain it; Katsuki laughs. The fear on his student's face begins to subside but his confusion stays intact. He doesn't make Midoriya wait long.
"All right, all right," he says, pulling himself together. "I'll help you feel more confident if I can. I'll give you extra worksheets to get used to the information. And when you have questions about specific things, you come to me and ask. Don't wait until you're overwhelmed."
Clearly surprised, Midoriya's jaw drops open slightly. He still looks nervous.
"Can I work on it here after classes? So I can ask you questions right away?"
The request sits uncomfortably, but he doesn't have a reason to turn him away. If the kid wants help, he'll provide that assistance as much as he can.
"Fine," he gives in. "I'll get some things ready for you to try out tomorrow."
He almost doesn't want to go back to his own desk, finding that he doesn't mind sitting beside him. But he looks back at Midoriya, who watches him carefully, unmoving.
"Can I stay here now? I'll work on other homework and I won't be in your way, I promise. I just don't want to—" He stops and appears to rethink his words. "It's nice and quiet here."
Katsuki takes a moment to squint at him. Something is clearly bothering him but he doesn't seem likely to share what it is. It's hard for Katsuki to part with his moments of peaceful solitude, but it doesn't feel right to turn him away.
"Fine. You can stay here while I do other work. Don't distract me."
The smile of relief that crosses Midoriya's face makes his sacrifice worth it.
-----
He comes back the next day, and the day after that. He's usually quiet, breaking the silence only to ask about the worksheets and assignments. Each day, something comes up that Katsuki forgets to hand over the sketchbook. Hanging onto it is a mistake, but there's always a distraction to keep it off his mind. And really, why would he think about it often? It's just one of many things students have left lying around for him to find.
And who can blame him for flipping through it occasionally? If it's sitting there and Katsuki can't focus on work anymore, it's only to idly pass the time. At least that's what he would say if anyone found him paging through it slowly, and it would be a usable excuse if he wasn't interrupted by Midoriya. They stare at each other blankly for so long it's almost comical.
"I guess I can stop looking for that now," Midoriya mumbles at last.
It's enough to make Katsuki snap out of it. The sketchbook is slammed shut with a loud smack before Katsuki shoves it towards his student without looking up at him.
"Go home," Katsuki demands weakly.
He doesn't wait for a response and still doesn't make eye contact. Wasting no time at all, Katsuki escapes as quickly as possible. He doesn't pause to rest or breathe or think until he's on the train heading home.
He's out of distractions, leaving him alone with the all-consuming thoughts of the exchange he just had with his student. Embarrassing. Katsuki could have easily been normal and sane by returning the sketchbook immediately after he found it. Instead, he held onto it, perusing it in quiet contemplation as if it was his own. Perhaps he felt entitled to it. After all, some of the drawings of him felt personal. But it's a weak excuse. Midoriya never crosses any boundaries and the art isn't inappropriate.No, it is personal. Just not to Katsuki. It clearly means something important to Midoriya, and Katsuki just took it away from him..
Over and over Katsuki has looked through that private assortment of art. The initial discovery was awkward, yes, but the real invasion of privacy is the way Katsuki has acted entitled to Midoriya's private work. He doesn't ever pry into his students' personal lives, doesn't particularly care at all, as long as they're safe. Midoriya probably thinks he's nosy, and if he does, he'd be right. He could even report Katsuki for stealing his belongings.
Irritation and fear warm him from the inside out. He itches to lash out or run away. For something to do, he lifts a hand to fidget with the strap of his bag, but he misses. It's not there. Most likely it's still next to his desk, forgotten after his rush to get away. He can't even leave it there – his ID, money, even the keys to his apartment are in there.
"Stupid fucking idiot," he grumbles to himself before begrudgingly getting up, beginning a shameful walk back to school. "The hell is wrong with me?"
At least he should be able to find it in peace and his thoughts can linger on how idiotic he feels. By the time he finds his bag, he's tired and out of breath, and absolutely ravenous. Food will have to wait, but at least nobody sees him acting like a dumbass this time.
"Sensei, I'm sorry."
Katsuki freezes. Not again. Hot shame and irritation flow through him in waves as footsteps approach. He wants to speak but he's so damn flustered he might burst into flames. He doesn't look, but he knows exactly who's standing near him.
"Take it back," Midoriya says quietly, holding out that damned sketchbook again. "I can tell it makes you uncomfortable, so please take it away. I promise I won't draw you again. Oh my god, I've upset you so much. I can tell because you're bright red and sweating, I'm so sorry."
Katsuki didn't realize he was sweating, but he does feel incredibly warm from running back to the classroom. If the warmth in his face wasn't enough, he's certain his insides are on fire. Heat coils deep inside, winding so tightly that it might break free any second to release the pressure. He hasn't felt this wound up since— oh, no.
"You need to leave." Katsuki is pleased to note that he doesn't sound flustered or whiny or anything of the sort.
"Stop trying to shoo me away! Please listen to me. I'm serious, I won't bother you at all and I'll do my best to not make you feel awkward but please let me apologize first."
Katsuki slumps into a chair, dropping his face into his hands, focusing on his breathing and trying not to make matters worse for himself. A drop of sweat rolls off his chin and hits his leg.
"It's fine. I don't care about that," he says through gritted teeth. He just needs to be left alone, definitely not with a student. "Just go. Please."
The vague sounds of Midoriya pacing around the room suddenly stop. Katsuki groans internally at how shaky he must sound. God, this heat feels like it will hit harder and faster than usual. Maybe it's because he's been agitated and running entirely on adrenaline for the last hour or two. Or it might be due to the alpha in his presence trying desperately to appease him.
Whatever the reason, Katsuki needs to be left alone before something incredibly stupid and irresponsible happens.
"Are you okay? You're sweating a lot. Do you need anything? How can I help?"
Katsuki lets out a breath of laughter that sounds strained even to his own ears. He needs a lot of things, and even more things would be tempting. A glass of water, a cool cloth on his face come to mind, but so does the thought of Midoriya's hands on him. They really are nice looking hands.
"You have to leave," Katsuki tries again.
He doesn't. Instead Katsuki watches his feet slowly move closer. If he looks up now, he's bound to say something damning that he won't be able to take back.
"Let me help you," he says softly. "Are you sick?"
A shaking hand brushes against the back of his neck. He shouldn't be touching his teacher like this, but Katsuki can't focus enough to tell him that when he's concentrating all his focus on restraining himself. Instead he lets out an unbidden whimper.
"Oh my god, you're hurt, aren't you?"
Katsuki really does laugh this time. It comes out breathy and strained but it relieves the tiniest bit of stress – just enough to slump slightly. Midoriya notices, steadying him with his free hand on Katsuki's shoulder.
"Dumbass teenager," he mumbles to himself before forcing calm into his voice. "Go home. I don't know how many more times I can say it."
He still doesn't move away. Instead he crouches down to force eye contact between them. Concern is evident on his face. It's sweet and endearing in a way that should be treasured by someone who isn't his teacher. Katsuki wishes he wasn't on the verge of doing something terrible to him.
"Oh." Midoriya stares. The eyebrows pinching together in worry give way to a blank look of shock. "Oh my god, you're–"
He doesn't back away but his eyes flicker around the room like he's going to find some miraculous solution. Katsuki, however, feels the warmth of his hands. The last shred of his self-preservation dissipates, washed away in the slick Katsuki feels dripping down his leg.
"Where's your phone? I'll call your mate and tell them to come for you."
"Don't have one," Katsuki admits, shaking his head and grabbing Midoriya's arm before he can consider leaving his side.
There's a reason why he avoids the topic whenever his students try to get personal information from him. Well, several reasons. Young alphas don't need any help making stupid decisions, not that Katsuki is much better. Midoriya opens his mouth, another question forming on his lips before Katsuki hisses through his teeth.
"There's nobody," he reiterates. "Leave, or you'll have to do something about this yourself. If you think you're up for it, Izuku."
The use of his given name strikes like lightning. Despite the surprise, he doesn't waste any time. He definitely has a higher capacity to think straight compared to Katsuki at this point because he gets up to lock the door. If it was up to Katsuki, he would have entirely forgotten the open door.
"Smart boy," Katsuki whispers.
The tips of Izuku's ears go red at that simple praise. He crouches again, staring openly at Katsuki's face. A gentle touch wipes away a trail of sweat making its way down his cheek. There's no hiding the smell when Katsuki feels a sudden pool of slick in his clothes. One whiff is all it takes before Izuku's face twists. It's the only warning he is given before he's roughly pulled onto the ground and his clothing is quickly torn away. He only hesitates when he sees Katsuki's slick-wet panties. His legs fall open in invitation and the apprehension vanishes, leaving only a sweet alpha losing control over his instincts.
Panties are shoved to the side and three fingers push inside before Katsuki can begin to explain what he needs.
"Hang on," Katsuki pants out, thrown off by the sudden intrusion. "I'm needy, but I'm not ready for that."
Twisting his own fingers around Izuku's wrist, Katsuki tugs him out lightly. The impending apology is palpable, about to fill the air, so Katsuki does the first thing that comes to mind. Watching his student's face carefully, he guides those fingers into his mouth, sucking slowly around them.
It's easy to put on a show like this when he knows there's more to come. He knows what to do when Izuku's dark eyes watch him carefully, methodically licking around fingers – a promise of what might come later. What he doesn't expect, however, is the way Izuku backs away, pulling his hand out of Katsuki's grasp.
Instead his fingers wrap around the back of Katsuki's thighs, pushing them up, up, up, until Katsuki's flat on his back and a tongue swipes lazily over his folds. It's exploratory, really, as though Izuku might be cataloging and analyzing the taste of his cunt. Small, curious licks that do little more than tease.
"Don't play around," Katsuki demands, already gasping a little for breath. Even his skin feels tense with need. "Do something."
Izuku listens well. Better than he does in class, because at least it's clear he's not distracted by sketching this time. The thought of class tickles at Katsuki's conscience, but not enough to make him stop. Certain that he'll overheat if he doesn't do something, Katsuki tightens his thighs against Izuku's head. He feels Izuku's gasp more than he hears it – a sudden suction that has him impulsively tightening even more. But then a hot tongue pushes inside, lapping up every drop greedily.
"That's good," Katsuki whispers, though his voice might go entirely unheard. "Keep going like that."
He can't help but slide his fingers through tangled green curls. Izuku looks good like this; a hand in his hair, pinned in place by Katsuki's thighs, his nails pressing sharply into the soft skin of his inner thighs. What Izuku lacks in finesse, he makes up for it in sheer eagerness. The ebb and flow of his tongue is enthusiastic. A series of sweet, involuntary moans send a vibration through him, and Katsuki can't help it. He tips over the edge of need and anticipation, digging his fingers into Izuku's scalp and heels into his back. With a slow, shaky exhale, he tries to calm down for a moment but Izuku is relentless.
He withdraws to breathe but doesn't allow any distance to form between them. Teeth nip at the tender skin at the crook of his inner thigh, softly scraping and closing around him but not biting down. At least not hard enough to mark him.
Katsuki's head is spinning and feels sated for the first time in ages. Before his instincts and heat can catch up and remind him that he needs more than tongue, he yanks at Izuku's hair, pulling him up.
"Come here," Katsuki demands, but Izuku follows his lead easily.
There's a question in Izuku's eyes that both of them ignore. Katsuki brushes a thumb over damp, swollen lips before surging up to claim them in a kiss. It's wet and messy and Izuku easily slips his tongue inside. He twists around, exploring and tasting eagerly. It's a mirror of his earlier ministrations, this time claiming the inside of Katsuki's mouth.
The shared taste of his own juices on their lips sends a shiver through him and draws out an involuntary groan from deep inside him. Grabbing onto the back of Izuku's neck, he roughly pulls up away, just barely.
"I'll need more than fingers or tongue to get through this."
Izuku stares blankly at him for a long moment. Growing impatient, Katsuki places a palm over Izuku's crotch. It twitches even through school uniform pants, and realization dawns visibly on his face.
"Is that okay? You'll let me do, umm, that?"
Katsuki can't stop himself from letting out a huff of laughter. At the hesitation, the request for permission, at Izuku's avoidance of talking about specifics after tongue-fucking him, at the absurdity of the situation.
"It's way too late for doubt, baby."
His eyes go so dark, the shining green disappears almost entirely. In the span of what feels like only a couple seconds, Izuku's clothes practically vanish in a desperate rush, catching around his ankles briefly. It's incredible how much a small endearment shifts the entire atmosphere. Perhaps he's just an uncontrollably horny teenager. Perhaps it's Izuku's own pheromones finally surging to meet the same level of need as Katsuki.
Or maybe, just maybe, the way their shared urgency is softened only by gentle hands holding onto Katsuki's waist tenderly means there's some degree of sentimentality there mixed with primal instinct. Gentle. It's enough to make Katsuki smile up at him genuinely.
The peaceful moment is interrupted by a surge of need that starts with the skin under Izuku's fingertips and rushes through him everywhere. Especially where he leaks through the panties that have slipped back into place. The relentless itch to have something deep inside him comes back in full force, his skin going taut and every muscle in his body tightens.
"You want to help me, right?" He doesn't have to wait; Izuku immediately nods. "Whatever you're thinking about doing to me, I need it. Do it. Now."
He doesn't want to admit how very little control he has over himself at the moment. He hasn't been touched like this in so long, and he has no memory of anyone ever holding him so sweetly. Before he loses himself entirely to the growing mountain of his own need, Katsuki needs more of everything.
"Yes, sensei," Izuku agrees easily, responding instinctively like he's in class.
He blushes immediately, dipping his head lower. It's adorable and irresistible.
"You like that." Katsuki can't help acknowledging it out loud. "Calling me sensei while you touch me – you like it."
That distracting shade of pink grows deeper, more splotchy, and he buries his face in Katsuki's neck. Hot breath on sensitive skin sets his nerves on fire.
"Come on, baby, don't be embarrassed. Show me how much you like it."
He nods without removing his face from Katsuki's neck, choosing instead to kiss him there and wordlessly lift Katsuki by the hips until their lower bodies meet. It's not a polished move. He's more focused on mouthing down the side of Katsuki's exposed throat and it takes a couple attempts to adjust their positions until he gets it right. When it is right, however, and the bare warmth of Izuku's arousal presses against him, it's wonderful, and he can't withhold a moan.
Izuku fumbles at the sound, his teeth scraping lightly at Katsuki's neck. Not breaking the skin but it's enough to elicit a shiver. Several more sloppy, wet kisses on his neck draw out more involuntary noises. It's dangerous to let those teeth get so close, but it doesn't matter. Not when it feels so damn good. The only thing that fully distracts him is the moment Izuku's entire cock shoves inside him. It's too much all at once but it's everything Katsuki needs. A fullness that almost satisfies that urgent instinct within him begging to be filled and fucked and bred.
Something isn't quite right about that, but it doesn't matter when he can't think straight anymore, not with the searing heat building between them. The points of contact – hands to waist, mouth to neck, naked cock against leaking cunt – engulf him with hot need. He wants to push away at the same time he needs to cling tightly to keep Izuku inside, but mostly he needs to move.
"That's it," Katsuki breathes out, using his last shreds of rational, restrained thought to persuade Izuku to do more than whimper into his neck. "Quick and easy, just like that. Can you move again? Need – I need more. Please."
He hasn't spoken this gently to anyone in so long, it's like stretching unused muscles. But he's desperate and the payoff is delightful. It's awkward but endearing as Izuku slips and stumbles in his hurry, but it's worth it when he withdraws far enough to slam back inside. Then again, and again, each thrust shoving Katsuki along the floor a couple inches. He plants a foot firmly on the ground, anchoring himself as he scrambles for purchase, scraping sharply down Izuku's back.
Another whine falls from Izuku's mouth briefly before the sound is muffled. He shoves in with an especially hard push and Katsuki feels him everywhere. The weight of Izuku's body over him is distracting. He doesn't have to move or think or breathe when Izuku's there on top of him, taking care of him. Losing himself to sensation, he drifts away while Izuku grows more and more frantic. But there's no missing the way something sharp and sweet pierces the skin at his throat. Katsuki fucking screams with it, losing every last bit of tension he didn't know he had been carrying. Where he was driftless before, where before he saw stars, now he's a supernova exploding into light and heat and energy spilling everywhere without concern. When he settles and comes back to himself – to Izuku and the way he's still spilling himself inside Katsuki – he's stardust. Weightless.
"How did you– what did you do to me?"
He breathes out a laugh and the immediate relaxed smile is impossible to erase. Izuku's face is still buried in his neck, but Katsuki doesn't push him. He's shaking lightly, and Katsuki tries to soothe him, rubbing circles down every notch of his spine. It doesn't help. If anything, he trembles even more.
"Baby," he says quietly, hoping Izuku still likes the word as much as in the heat of the moment. "Talk to me."
He shakes his head, so Katsuki waits, breathing slowly and hoping Izuku will mimic him enough to calm down. He does, just a little, but it comes with several small sniffles and he shakes his head again.
"Are you crying?" Katsuki asks.
The gasped sniffle and aggressive shake of his head smacks Katsuki in the face with the reminder of Izuku's age. He's definitely crying.
"I'm sorry," he finally chokes out. "I don't know what I was thinking. I ruined everything, I'm so sorry."
Katsuki bites back a chuckle as much as he can, but amusement is clear in his voice. He lifts a hand to the nape of Izuku's neck, holding him close with what he hopes is a comforting touch.
"You really do apologize a lot. More than necessary."
Izuku doesn't say anything, but his mouth opens against Katsuki's skin like he's trying. He shifts slightly, sliding a hand upward until his fingers brush over a particularly sensitive spot on his neck. The featherlight touch feels like an electric jolt streaming through every nerve ending on his body.
Katsuki hisses sharply, shocked by how sensitive he is. It's distracting. Those gentle fingers trace along some imaginary pattern on repeat. It's sweet. Tender and gentle, even as Izuku continues mumbling increasingly desperate apologies into the delicate skin under his jaw. There's a tingling intimacy in the gesture that doesn't outweigh Katsuki's worry.
"Tell me," he insists, easily falling into a tone he usually reserves for a classroom filled with misbehaving teenagers. "Tell me why you're apologizing."
"For this," Izuku says with a sniffle.
He pokes harder at the same spot he was just tracing gingerly. It doesn't click right away. Whether he's slow to understand due to the heat-induced fog in his brain or post orgasmic bliss, he doesn't know what Izuku's talking about until he kisses the side of Katsuki's neck. Wet with tears, there's a palpable shame in the careful slide of lips and teeth on skin.
The memory comes back in a flash and it's already permanently ingrained in Katsuki's mind – a claim. Amidst need and want and so much damn heat between them, Izuku had claimed him.
"Oh. Oh, fuck."
He drops his head back on the ground. Neither of them move for a long moment – Izuku murmuring desperate pleas for forgiveness while Katsuki stares blankly at the ceiling, unthinking. The stupor passes seconds – or maybe hours – later, and Katsuki twists his own hand around Izuku's wrist.
"Stop," he demands, and Izuku obeys immediately. "Stop apologizing. Stop all the pity shit. Just stop."
He tugs away lightly, but Katsuki holds him still.
"I didn't tell you to leave, I told you to stop. You're a kid – god, you're a fucking kid. You should go home. Maybe you'll even forgive me one day."
This is a mess. He should have been more firm, made Izuku listen, made him listen. Instead he let instinct and arousal take control, and now he's bound to an alpha who should be discovering himself – not beholden to the needs of his teacher. Fuck. He could be reported. He's doomed as an omega but his career is bound to be destroyed when Izuku rightfully tells a parent or another teacher about what's happened.
A sudden kiss on the mouth snaps him out of overthinking. Thoughts and time alike stand still as Izuku cups his face between both hands and kisses him like he's precious. When he speaks, he stays so close that his lips move against Katsuki's with every syllable.
"I'll only leave if you tell me that's what you want," Izuku offers quietly.
He doesn't want that and he can't force himself to come with an excuse. His mind reels but he can't convince himself to give up the one thing he hadn't realized he needed. Not like this. Not when Izuku stares at him sincerely like he truly wants to be here with Katsuki.
It's unbelievable. All of it. From forgetting about his own impending heat, to this moment where Izuku doesn't want to leave him alone, the situation is absurd. Yet there's an unnerving peace about it. Unnerving because he should never have allowed this to happen, but peaceful because he's content with the results. Instead of speaking a word, he wraps his arms tightly around Izuku's back.
There will be consequences for this moment of weakness, but for now, he's actually happy.
-----
Eventually they're forced to move. The most urgent part of his heat having passed, the floor is uncomfortable and they know anyone could find them like this. When Izuku finally, slowly pulls out of him, Katsuki gasps at the loss. He should know better and expect the shift, but it felt natural with Izuku inside him, like he was finally whole only to have a piece of himself ripped away.
"Don't," he pleads, reaching up to Izuku who's already standing over him.
Izuku's there in a heartbeat, but instead of curling up against him, he scoops Katsuki up into his arms.
"I'm not leaving you alone," he promises. "I'm taking you home. You just–"
He drops his head, glancing away, sheepish about whatever he wants to say despite everything that's passed between them. Katsuki squeezes his arm, as quietly supportive as he can manage.
"You just have to tell me where you live."
Katsuki snorts out his sudden laughter, burying his face into Izuku's neck, unbelievably enchanted with him.
"Help me back into my clothes first, then I'll tell you where I live and even where I'm taking you to bed with me."
An embarrassed flush is starting to become Izuku's most consistent expression, but he moves so fast he nearly stumbles. More than once.
-----
The world doesn't implode after those hours spent together. In fact, everything is nearly the same. His skin feels wrong without Izuku touching him and the hidden mark on his neck stings, but his students act the same way they always do, and there's no lingering scent from the mess they made on the floor. A tinge of irrational sadness tugs at him, mourning the absence of their combined smell.
But Izuku catches his eye, smiling widely, and suddenly the loss doesn't matter anymore. There will be plenty of future opportunities to experience together. For now, there are no consequences in sight, and he plans to keep it that way.
"Sensei, can I talk to you about our homework after class?"
Katsuki bites the inside of his cheek to keep from grinning up at Izuku. The hopeful look on his face is endearing and Katsuki wants nothing more than to kiss him. Instead he nods wordlessly and Izuku finds his seat. Touching his neck casually, it's hard not to watch the way Izuku's eyes trace the motion.
Maybe that social implosion isn't so far off, or maybe it won't happen at all. There's so much uncertainty but he's fully confident that, despite their circumstances and differences, Izuku will be there at his side no matter what.