Thread by @useless_donut, Couldn't stop thinking about a/b/o alpha/alpha shinzawa spending their ruts together and [...]

Couldn't stop thinking about a/b/o alpha/alpha shinzawa spending their ruts together and how Shinsou might struggle to get his instincts under control, how Aizawa probably is delighted to "help" him submit...

and now it's really long and also a thread :')

Shinsou / Aizawa

cw: a/b/o content / age gap / aged-up characters / student-teacher relationship but like way in the past? / violence or rough sex / probs some blood it's a/b/o they're bitey lol / fluff :) /

nsfw explicit content

Shinsou never quite figures out what sets him off, but one moment they’ve been on stakeout for 8 hours, trading sarcasm and nihilism, and the next, his teeth are snapping in Aizawa’s face. The instinctive, jagged aggression is harder to push down than normal.

But then, it doesn’t really matter. Aizawa’s massively unimpressed expression will put most alphas in their place, and Shinsou is no different. He blinks at Shinsou slowly, eyes narrow and catlike. Shinsou shuts his mouth with a snap.

“Don’t know what' gotten into me,” Shinsou mutters, looking back out the windshield. He knows better. Posturing like this at his mentor is pathetic, but his rut is coming up and the van they’ve been cooped up in stinks of alpha. Pheromones crawl over his skin like oil over water,

telling him to fight or fuck pretty much anything that moves. He wants to give in. It’s pathetic.

Aizawa snorts softly. “I think I have an idea,” he says drily, gaze flicking up and down Shinsou’s body. It’s an effort not to react, but Shinsou’s a pro.

After nearly 10 years as an underground hero, practically nothing fazes him. Aizawa, though, has always been an exception.

It’s not until they’re in a shitty Yoshinoya after their shift that it comes up again. They fit in with the night crowd easily in their stakeout clothes.

As always, they look somewhat similar. Both of them in ratty sweats, Shinsou sporting an ancient crewneck sweater with an outdated meme on it and Aizawa in a massive, stained hoodie. Shinsou watches him push a piece of beef around with a single chopstick, looking sallow and

exhausted in the Yoshinoya’s cheap yellow lights.

“Did you take time off,” Aizawa says abruptly. Shinsou follows his gaze out the window. It’s 3 AM, and not much is happening. The occasional pedestrian scuttles down the street, obscured by the blur of traffic lights in rain.

“Yeah. Thursday," Shinsou says.

Aizawa grunts in reply. The beef makes another chopstick-propelled circle in his bowl. Then, “I guess that’s why they gave me such a hard time, if you were already taking off too.”

“Hm?” Shinsou finally looks back at him.

Looking at him, this late, this close… it feels a little dangerous. Aizawa smells like he always does, but tonight it’s strong. Heady. Whatever store-bought suppressants they’d worn are fading after a long stakeout, and all Shinsou can process is his goddamn /scent/.

Aizawa smells like stargazing, like a night spent on a lonely rooftop, like wet cement and empty urban streets.

Shinsou jerks back, realizing too late he was leaning in. Aizawa runs a hand through dark hair, pushing it ineffectively out of his face.

“I think we’re synced,” Aizawa says, then yawns, jaw popping. “Makes sense; we’ve been working together a lot lately. I guess we're close enough.”

Synced. Synced? Shinsou fights past the haze of exhaustion and Aizawa’s night-city smell to realize he’s talking about their ruts,

of all things. Then he’s suddenly, painfully aware that they’ve never talked about things like this before.

Shinsou swallows hard, trying to appear nonchalant. “Did you uh, get your time off request approved?”

“Finally. Got the notice today. Guess a week alone will do me good.” Aizawa shoots him a bored look, digging at something between his teeth with a toothpick. “I'll finally get a break from all your smartass backtalk.”

“You like it,” Shinsou says immediately, dropping his chin into his hand, elbow on the countertop. Is he flirting? He can’t be. Not with Aizawa, even if he knows their scents are mixing, rubbing up against each other like friendly cats. Maybe they’re close, but not like /this/.

Aizawa doesn’t deign to answer. Shinsou tries again. “So, a week alone?”

Aizawa’s chin sinks to his chest like a turtle, disappearing in the folds of his hood. “I’m an old man, kid. Don’t need to go crazy anymore. I’ll leave crap that to you.”

“You’re literally just 42."

Shinsou can’t quite look away from the shadows pooling at Aizawa’s throat, the ever-present scruff. Something feels different tonight. Maybe they’re both tired, worn down enough that they can’t quite fight down the chemical cocktail their bodies are determined to put out…

“I’ve got some match-made omega scheduled in," Shinsou says. It sounds so clinical when he says it like that, and Shinsou supposes it is. He can’t even remember the name of the woman he’s been assigned. Aizawa doesn’t seem to care either way, instead stuffing the last piece of

beef into his mouth. Shinsou is abstractly happy to see him eating something that isn’t a juice pack.

“But I can still cancel,” Shinsou says, watching Aizawa’s mouth as he slowly chews. He barely knows what he’s saying, but the air between them has never felt like this.

It could easily just be Shinsou’s rut coming on early, but everything smells like anticipation. Like the lines between them can be blurred like ink on skin.

And fuck, Shinsou is closing in on thirty and he can take a goddamn chance. He can always blame it on hormones later.

Probably.

Aizawa will certainly mock him mercilessly for it, but Shinsou rather likes it when Aizawa gets mean.

“What,” Aizawa says, blinking at him. Shinsou can see half-chewed beef in his mouth. Fuck, he wants to kiss him.

Is Shinsou aroused? Does Aizawa know? He has to, he’s got a working nose, and if Shinsou is feeling this /much/, he must reek of it.

What does he smell like to Aizawa? He leans in, meeting Aizawa’s flat black stare.

“I can cancel,” Shinsou says slowly, intentionally imitating Aizawa’s talking-to-idiot-students voice, “and then you don’t have to be alone.”

“What?” Aizawa repeats, chewing still. Shinsou grits his teeth, his mind made up.

Besides, he’s too riled up to back down now, and he doubts his alpha would let him even if he wanted to. Which he doesn’t, because Aizawa isn’t stupid and he’d have shut Shinsou down /long/ ago if he was completely disinterested.

“You don’t have to be alone,” Shinsou growls, “if you spend your rut with me.”

Aizawa blinks once, processing, then his eyes shoot open as he chokes violently on his food. Shinsou watches, vaguely delighted he’s had any effect on the other man. It’s maybe thirty second of hacking before Aizawa gets it down, then glares daggers at him.

“Shinsou,” Aizawa says, “do you know what you're saying? You’re an alpha. So am I.” His voice is so deep and dark that Shinsou wants to drown in it.

“It’s been done,” Shinsou says instantly. Aizawa’s chin lifts, a subtle gesture of defiance.

“I was you mentor—”

“You were. A /decade/ ago. It’s just an offer, /Sensei/.”

Aizawa takes a long drink of water, throat bobbing as he swallows. Shinsou can’t think of anything except how he hasn’t been rejected yet.

Aizawa looks at him sidelong. “You still call me /that/.”

“Suck my dick,” Shinsou says, just because he can. Aizawa lets out a short, sharp laugh and drops money on the table.

“You wish... apparently. Don’t bite off more than you can chew, kiddo. See you at headquarters tomorrow.”

Shinsou watches him walk out the door in a daze. He… still hasn’t been rejected. Then he’s stumbling off his stool in haste, chasing after Aizawa.

Shinsou catches him outside on the sidewalk, and the fact he hasn’t already melted into the night is practically an invitation.

“You think I can’t take it?” he says to Aizawa’s back. Aizawa stops and turns, hood pulled up. His face is shadowed, damp hair plastered across his face.

Aizawa crooks a finger. Shinsou steps up to him as surely as if he’d been trapped in Aizawa’s capture weapon.

Out here, their scents are dispersed, less powerful, but the calculating look Aizawa gives him still has heat rolling up his spine. Aizawa isn’t exactly expressive, but Shinsou has known him a long time and this—

This is far, far further than he’d ever dreamed of getting with the older man. Aizawa meets his eyes.

“You think you can?”

“I—”

“You’re a young, strong alpha,” Aizawa says derisively. “You really think it’s going to be so easy to submit? Bend over like a bitch in heat?”

“I’m not a fucking animal,” Shinsou snaps, stepping in. They’re only inches apart. Shinsou feels the heat of his presence acutely, despite the chill of rain. “I’m a goddamn adult. I can control myself, and so can you. You’ve /seen/ it.”

“Sex is different, and a rut’s even worse,” Aizawa says, hands in his pockets. Unarmed, like Shinsou isn’t even a threat. It’s practically an insult, and Shinsou feels the need to fight like an animal inside him, digging in its claws, hissing in his ear and telling him to fight.

Or fuck. But he does nothing except smile slightly, because he’s learned to school his expressions from the best. From Aizawa.

He pulls out his phone and brings up the number to the match agency, pushing it into Aizawa’s field of vision. “I’ll call and cancel right now.”

Aizawa stares at him in silence, in the calculating way that tells Shinsou he’s making a decision. There’s an occasional rush of wind as cars pass by, but Shinsou says nothing. Cold rain runs down his face, dripping down his scalp.

This feels like a test. It almost certainly is.

Finally, Aizawa steps in. The scent of his arousal is sudden and sharp, like too-hot sake at midnight, and Shinsou is swimming with it, drunk on it.

“You think you can control yourself,” Aizawa says flatly.

“Yes.” Shinsou’s reply is quick, breathless, because hesitancy will scare Aizawa away faster than anything. Aizawa’s dark eyes sweep him from head to toe, critical, evaluating. Shinsou’s never wanted to pass one of his tests this badly.

“Hm. I guess we’ll see.”

“Wait, does that mean—”

“I’d cancel on your omega now, if I were you,” Aizawa says, eyes narrowing. “It’s rude to lead people on.”

Shinsou stares. Stares so long that Aizawa’s expression morphs into that awful, gleeful smile. “Scared off already?”

“So you’re going to… really…” Shinsou chokes out. Even if he’s wanted this for as long as he knew how to /want/, being successful had never once seriously occurred to him.

This is unreal.

Un. Real.

“Email me your address. We can work out specifics,” Aizawa shrugs, pulling the strings of his hoodie. It scrunches around his face, tufts of black hair sticking out around the edges.

“Email?” Shinsou turns sarcastic because he’s on autopilot, and he left his brain somewhere

in his dick with no chance of retrieval. “Seriously? Can’t I just text you?”

“Hey, you’re the one who wants to fuck an old man,” Aizawa grins, his teeth a white crescent against the night. “Don’t bitch, or I’ll make you fax it.”

He’s already rounding the corner by the time Shinsou thinks to shout after him, “You’re only 42!”

Shinsou walks the entire way home, dumbfounded and wide-eyed, soaked to the skin but still somehow hot all over.

It doesn’t sink in until he walks in his door and realizes that his apartment is a fucking mess and he’s inviting /Aizawa/ there to /fuck/ in a /week/, and his life is a shitshow, but the best shitshow possible.

He cleans until 6 AM, spends twenty minutes regretting

his life choices, sleeps for two hours, and is on patrol the next day like nothing fucking happened.

Neither of them bring it up for the rest of the week. It’s torture for Shinsou. He usually has better control over himself, and even the days leading up to his rut typically leave him relatively unaffected.

Then it’s Thursday. Shinsou’s house has literally never been cleaner.

There’s snacks everywhere, food deliveries scheduled (which strict instructions to leave things at the door), and several new blankets.

Aizawa shows up at 6 PM sharp, just as they’d planned. Over email. Extensively. Shinsou is only freaking out a lot.

Yeah. Shinsou is freaking out. Sort of definitely reassured, but still completely freaking out because it’s /Thursday/ and now Aizawa’s knocking on his door. Shinsou can see him distorted through the peephole, a massive duffle bag slung over his back.

He’s wearing a white long-sleeve shirt and some jeans. It’s almost dressed up, and Shinsou feels absurdly touched. Mostly, he just feels absurd. The feeling doesn’t dissipate as he opens the door, and Aizawa walks in.

Shinsou nearly loses his balance, rocking back to lean against the wall because Aizawa forewent scent blockers and. And. Shinsou can’t really think of anything but him, of his scarred face and curling black hair and how he smells like every silent walk through downtown and—

Aizawa brushes past him, heading for the living room. Shinsou remembers abruptly that he’s been here before.

“You cleaned,” Aizawa says, dropping his things on the couch and unzipping the bag. Shinsou watches, speechless, as he upends it over the coffee table.

An entire sleeping bag, maybe a hundred juice packs, loose papers, and a random assortment of clothes spill everywhere. Then he looks at Shinsou over his shoulder, like a cat that pushed a glass off a counter.

It’s impossibly seductive. Something has to be wrong with Shinsou.

“Make yourself at home, Sensei,” Shinsou says faintly.

Aizawa glares. “You know what I’m like.”

“I do.”

“It’s not too late to back out, kid.”

“Do you /have/ to call me kid?”

“Do you /have/ to call me Sensei?” Aizawa says, matching Shinsou’s tone perfectly.

“I’m not backing out,” Shinsou finally says. He carefully steps around juice packs until he’s right in front of Aizawa. “The opposite, really. Sensei.”

“What’s that?” Aizawa’s chin tilts up to him, unafraid but also undemanding. They’re so close, it’s practically unbearable.

“Kid,” Aizawa adds, but his voice has dropped to a whisper.

Shinsou’s going to kiss him. He has to. They’re literally here for a week of fucking, but Aizawa still feels so off-limits. Several day’s worth of email-based planning has /not/ prepared him for this feeling.

“I’m all in,” Shinsou says, voice low in his throat. He thinks he sees Aizawa shiver, like he’s attracted to Shinsou. Like Shinsou can affect him. And maybe Shinsou has noticed his lingering gaze before, always quickly aborted. Still, he’d never hoped to catch Aizawa’s eye.

Aizawa does nothing, because of course the first move has to be up to Shinsou. He raises a hand slowly to Aizawa’s face, the forbidden nature of the movement weighing him down. It feels like an eternity before his palm rests on Aizawa’s scratchy cheek.

The universe shifts when Aizawa’s eyes drift shut, leaning into his touch. This is better than everything. Better than coaxing in a feral cat, than early morning coffee, than sleeping 24 hours straight, and Shinsou finds himself leaning in, pressing his lips against Aizawa’s.

It’s a miracle when Aizawa kisses him back, lips parting slightly under his. He can feel his pulse thudding in his ears, urging him on, to take more, claim more, take everything that Aizawa will let him take. It would be so easy to get lost in the feel of his mouth,

the scruff on his cheek prickling against Shinsou’s palm—

Pulling back takes more effort than it should. Shinsou steps back and tries to calm the rut scratching at his ribcage. God, he wants to take and /take/ everything he can get but—this can’t turn into a fight for dominance.

If he can submit to anyone, it would be Aizawa. God knows he’s imagined it thousands of times, especially in the last week, stretching himself open to prepare for a knot his body isn’t made for.

He’s never wanted someone this badly, he’s sure, and he wasn’t really /supposed/ to go into rut until tomorrow but, hell, he can feel the heat of it in his chest, embers burning for Aizawa alone. He might go mad if he has to wait any longer.

“You reek,” Aizawa says, stepping away. Shinsou blinks after him, watching as he flops onto the couch.

“Like what?”

“What?

“What do I smell like?”

Aizawa stares, then runs a hand over his hair, pulling out his low ponytail.

Shinsou swallows hard, watching the way inky hair cascades around his shoulders. Aizawa manages to do the simplest things in ways that feel impossibly erotic.

Or maybe Shinsou is just going to hit his rut early.

“A couple years ago I was on a sting op in Seattle,” Aizawa says, staring unfocused off into the distance of Shinsou’s living room. “Weapons trafficking, nasty op. I was undercover, working 18-hour days. Fucking place was miserable, raining every goddamn day.

Hadn’t seen the sun in weeks. Found this little café one day. Got a latte. I was sitting on the steps out front, sitting on wet, cold concrete. I was exhausted, freezing, and damp.”

“I smell like a shitty undercover gig?”

Aizawa shoots him a look, meeting Shinsou’s eyes with an intensity that punches the air straight out of his lungs. “Do you want to know, or not?” Shinsou makes a show of shutting his mouth, and Aizawa continues. “Anyway, the cloud cover broke for a moment.

It was a little past dawn, and everything was suddenly… I could see the sunrise over downtown, and the air was clean and cold from the rain. That’s what you smell like. I had a latte and the sun had come out, and for one moment I felt like everything in the world made sense.”

Shinsou is stunned, unable to speak for a moment. It feels like Aizawa revealed more than he meant to, because his shoulders hunch, eyes flicking away from Shinsou. Shinsou swallows, pulling himself together.

“Sensei, that almost sounds romantic.”

Aizawa buries his face in his hands with a groan. “Shut up. I’m horny.”

If hearing about how Aizawa sees his scent had rocked him, this is worse. It doesn’t matter that Shinsou already knows exactly what Aizawa is here for.

The sudden shift to seeing him in a sexual context has him reeling, mouth running as if he hadn’t spent years perfecting control over his vocal chords.

“Shit. That’s. Fuck. That’s hot,” Shinsou stammers, making his way to the couch.

Even thinking of him in a sexual manner felt taboo until days ago, and seeing it in person is too fucking much. Aizawa looks at him sidelong, eyes shadowed by thick, short lashes.

“Is it?”

“So hot,” Shinsou repeats, leaning in. Aizawa sits back, making space for Shinsou to climb on his lap.

“Maybe we should try this before we’re too fucked up on hormones,” Aizawa says, his voice deep and gravelly. Sexy. Undeniably. Maybe Shinsou is losing his shit, a little.

“Probably,” Shinsou agrees, dropping his weight on his legs. Aizawa groans, head dropping back.

“God, you’re heavy,” he says, baring his teeth, “And I have—I, you know. Prepped. Have something. You know. In.”

Shinsou freezes. The implications…

“Wait, you thought—”

“You’re not my first alpha,” Aizawa says, even as his hips twitch upwards. “You talk a big game, but I didn't know if you'd be able to bite the bullet. So to speak. It's just practical to be ready to go... either way.”

“You’re fucking with me,” Shinsou says. “Fuck you, I’ve been prepping all /week/ for this.”

Aizawa frowns at him. “Oh.”

“Yeah.” Shinsou says.

“So we both expected—”

“Yeah.” Shinsou sighs, rubbing his face.

They sit for a moment, suddenly aware they’ve revealed a lot rather quickly, and awkwardness creeps in around the edges of the living room. Aizawa shifts uncomfortably underneath him. Shinsou thinks about how nothing in his life could have prepared him for this moment.

“You know, there’s a meme about this,” Shinsou finally says into the silence.

“Don’t—”

“And so... they were both bottoms.” Shinsou grins down at him. Aizawa shoves him off his lap, standing with a groan.

“I /will/ leave if you keep talking like an idiot.”

“Will you though?” Shinsou lies back on the couch, watching the way Aizawa pulls his shirt over his shoulders, the white fabric shifting over a lean, well-muscled back patterned with scars.

“Don’t test me,” Aizawa grunts, tossing his shirt on the floor before turning to face him. “My fleshlight doesn’t talk back nearly as much as you.”

The image of Aizawa on a bed, thrusting into a toy completely obliterates every thought in Shinsou’s mind. He’s still sitting on the couch like an idiot by the time Aizawa’s standing there, completely naked, staring at him.

“Christ, I know I’m not much but I expected /some/ reaction,” Aizawa says, one side of his mouth curling into a smile. Shinsou drops out of his daze like he stepped off a cliff.

“No. No. You’re,” he chokes out, words failing him for once in his life.

It’s /Aizawa/, lithe and muscular, dark hair gathering on his chest, trailing down his stomach, framing his dick. Thick. Thick dick. Shinsou can't stop staring.

“What?” Aizawa asks, reaching up to scratch his scalp. “Come on, let’s get going while we’re lucid, hm?”

Shinsou watches in an incoherent daze as Aizawa walks over, sits on the couch, rolls onto his knees as he starts working a plain black plug out of his ass, then promptly depositing in a box clearly meant for that exact purpose. Practical. Functional. Shinsou's brain is breaking.

Aizawa sighs, stands, digs around in the mess for a huge bottle of lube, gets back on the couch, and picks at the plastic on the lid.

“Hot,” Shinsou says, because it takes that entire time for his brain to catch up. Aizawa’s disbelieving snort is loud in the quiet evening.

“Took you that whole time to figure it out, huh?”

“Hot, so—you look so good, Sensei, I, fuck, I’m,” Shinsou rambles, aimlessly moving towards him. Aizawa stops him with a warm hand on the center of his chest, and, shit, they’re touching. His hand is on Shinsou and...

“You’re a mess,” Aizawa says, eyebrows raised. “Pull yourself together, kid. Try to last more than a minute.”

“Hnng,” Shinsou says, because maybe he’s 27 and maybe he’s had plenty of sexual experience but, god, never with someone like this.

Never with someone he so desperately cares about, respects so much.

“Thirty seconds, then?” Aizawa says in a mock helpful tone. Shinsou swallows hard, head roiling with hormones and arousal and sheer disbelief that this is his life and he’s living it.

“Uh, let’s find out.”

“Smooth. But fine. Go ahead, impress me.” Then he /presents/ like a fucking omega, all face down ass up and Shinsou has never seen anything hotter in his entire life and has absolutely no idea how Aizawa can make submitting look like a walk in the park.

Already, Shinsou’s instincts are screaming at him to mate, claim, take and take and—he breathes out slowly. Aizawa is obviously in control of himself. Shinsou can be too.

He puts a tentative hand on Aizawa’s ass, thrilled with the way he shivers under his hand.

He bites at his lip mindlessly, marking the curve of Aizawa’s back, patchy with hair and scars, the black curls dripping over his shoulders.

“Any day now, champ.”

“Now you’re just /trying/ to annoy me.”

“I’m trying to get you to fuck me, actually,” Aizawa says drily.

Shinsou presses his lips together because Aizawa is in one of those moods, and if he doesn’t want to just sass all day then one of them needs to shut up. So he strips off his clothes, tosses them carelessly on top of Aizawa’s things, then positions himself between Aizawa’s legs.

Unreal.

“Get on with it. Been prepped for ages.” Aizawa’s voice is gruff.

“Right.” Shinsou suppresses the urge to say something stupid like ‘here goes,’ and instead places his hands on Aizawa’s ass, inching forward until his dick is pressed up against him.

He’s already half-hard, and it’s almost dizzying how quickly this is turning him on. But it’s /Aizawa/. His breath hitches, tripping in his throat, as he rocks against him slowly. Aizawa says nothing, but Shinsou takes comfort in his steady, measured breathing.

Shinsou grabs lube, cringing at the cold temperature, and then he’s ready. Nothing else to do. No reason to postpone, and Aizawa is obviously impatient. He’d like to imagine this as some kind of point of no return, but the reality is that they passed that long, long ago.

He takes a deep breath, grips himself, and pushes the head of his dick into Aizawa’s ass. Aizawa grunts, shoulders tensing, but otherwise accepts it and—

“Fuck, you’re tight,” Shinsou sighs, unable to help the way he rocks forward. He pushes in slowly, so distracted by how good it feels, so tight and hot and, fuck. Aizawa’s grabbing at the couch, arms flexing, and maybe it isn’t as easy for him to submit as Shinsou assumed.

Shinsou’s trying to be nice about it, moving so slowly it’s practically torture when every inch of him that touches Aizawa feels like heaven. But, finally, he bottoms out, bending over Aizawa’s back to wrap his arms around him, just to touch him.

He’s finally allowed to /touch him/, run his hands up his stomach, his chest. Just holding him, tightly enough that he can hear Aizawa’s steady heartbeat, hear the long sigh he lets out.

Shinsou buries his face in the valley between his shoulder blades, nose tickled by Aizawa’s hair, and finally grinds forward. God, it’s tight, more than he’s used to, and it’s tying him up in tight knots of pleasure.

Then Aizawa groans.

Groans like he feels /good/, hips pushing back against Shinsou. That alone nearly undoes him, but he finally starts to move, listening for every tiny hitch in Aizawa’s breath like his life depends on it.

“You feel,” Aizawa breathes out, “good.”

It’s praise. It’s fucking approval, and the heady rush Shinsou gets is enough he doesn’t even notice the way he’s stiffening, balls tightening as he suddenly comes from just three words.

He whimpers into Aizawa’s back, hands grabbing at his chest, hips twitching as he pushes deeper and he spurts helplessly into him, riding out his orgasm. Aizawa’s frozen, still, until Shinsou’s ragged breathing calms.

“I was actually joking about the thirty seconds thing, Shinsou.”

“Shut up.” The words are muffled against Aizawa’s skin, and Shinsou would feel more embarrassed if he didn’t feel so damn good. “You’re the one who had to sound like fucking sex on a stick.”

“I said /one/ thing.”

“Sh,” Shinsou tells him, tightening his hug, adjusting the angle. Aizawa is tight around him, perfect really, and his knot’s already well on its way to full size.

Aizawa tries to pull away. Shinsou’s tugged along with him, whimpering a little at the sensation.

“Oh,” Aizawa says. “Goddamn it, Shinsou. How long are we gonna have to sit here, now?”

“Hm, a while,” Shinsou says, smiling against Aizawa’s skin. He's nearly delirious with afterglow, and he probably won't be able to think clearly until his knot deflates enough to pull out.

“I’m young and virile, remember?”

“I hate the youth,” Aizawa grumbles. “Christ, are you still getting /bigger/?”

“Isn’t it great,” Shinsou says dreamily. Aizawa huffs, shifting uncomfortably.

“It’s big, you shit. You’re fucking—are you sure it’s supposed to be so—”

“What?”

“Nothing,” Aizawa says, face dropping back onto the couch. “It’s uncomfortable, okay? I’m not fucking made for this.”

“Thought I wasn’t your first alpha,” Shinsou teases happily.

He’s come inside his lover, holding him in his arms… he’s happy, content.

“You’re definitely the most annoying one,” Aizawa tells him. He sounds a little breathless.

“I try,” Shinsou purrs.

The words rumble in his chest, the sound rough and unfamiliar and holy shit, he’s actually /purring/. Shinsou doesn’t purr, but suddenly he can’t stop, rubbing his cheek on Aizawa’s hair like a cat, hands stroking mindlessly over his chest.

The urge to take care of him is overwhelming, and all his attention is trained on Aizawa, enough that he can’t miss the way Aizawa’s breaths are getting shallow, coming with tiny, uncomfortable sounds. Shinsou frowns, carefully shifting to get a look at his face.

“Sensei, are you alright? It shouldn’t be much longer.”

AIzawa turns his head to look at him, saying nothing. His face is flushed, eyes glassy, the corner of his mouth wet with drool. Concerned, Shinsou leans forward, unintentionally pushing deeper into him.

Aizawa’s eyes shoot open as Shinsou moves, and then he /moans/.

Aizawa’s not hurting. He’s getting off on it. Shinsou’s suddenly dizzy with a second wave of arousal, and even if he definitely can’t come again this fast, he’s unbearably turned on.

Still, he feels strangely perverted, like Aizawa isn’t his to lust over. Even if he’s literally moaning on his dick. Shinsou breathes in deep, savoring the smell of Aizawa’s skin, the lingering scent of early morning and sleepy desire.

He finds himself kissing his way up Aizawa’s spine, murmuring, “Does it feel good, Sensei?”

“Big…” Aizawa sighs, shifting again. Shinsou realizes with a jolt that he’s fucking himself on Shinsou’s knot with tiny, precise movements.

Heart pounding, Shinsou lets his hands wander back down Aizawa’s chest, following the trail of hair over his abs, to brush against his dick. Aizawa sucks in a breath, back stiffening.

A good sign? Shinsou takes a chance, wrapping his hands around AIzawa’s cock.

He’s hard, thick, the tip of it already wet with precum. It feels intimate. Shinsou’s heart aches with it, how close they are, how much he cares, and how badly he wants to take care of him—hormones. Hormones, it's all hormones.

He’s just full of goddamn alpha rut hormones, and they’re making him protective. Not for the first time, he wishes he could have been born something less irrational.

But Aizawa’s dick is still hot in his hands, and his choked-out moan as Shinsou starts to stroke him is enough to empty Shinsou’s mind of anything else except the feel of skin on skin.

“F-fuck,” Aizawa mumbles into the pillow, “more, fuck, Shinsou—”

Shinsou probably underestimated just how much his continual desire to please Aizawa would affect him, because suddenly nothing exists anymore except for Aizawa and his soft, barely-controlled grunts of pleasure.

Then Aizawa’s hands wrap around his, squeezing, guiding him to move faster. Shinsou’s natural instinct to seize control, have his way, is waylaid entirely by his fascination with Aizawa simply getting off.

Aizawa comes in probably the most anticlimactic way, with a drawn-out groan that’s punctuated as he shoves his face into the couch cushion. Shinsou adores it, even if Aizawa’s grip on his hands is painfully hard in his attempt to apply pressure to his knot.

Aizawa’s pulse beats under his fingers, throbbing as he spills on the couch. His hands are hot on Shinsou’s, rhythmically milking himself through his orgasm, back tense and shaking beneath Shinsou’s chest.

God, it feels like it goes on forever, and it kind of feels like Shinsou’s finger bones are being ground together under Aizawa’s crushing grip. But Aizawa finally stills, face still on the couch, hands dropping from Shinsou’s as he goes limp. Shinsou’s happy to follow suit,

draped over Aizawa’s back like a blanket as they gradually relax.

Eventually, Shinsou’s able to slide out. Now that he’s not high on post-orgasm haze coupled with the whole dick-in-your-hero’s ass thing, he’s sort of mortified. Two thrusts. Two thrusts is all it had taken?

At least his mate seems satisfied.

Mate? Shinsou stands abruptly, grabbing his shirt to wipe at himself. Aizawa grumbles something incoherent, still face-down and limp. Shinsou makes a vague excuse and hides in the kitchen on the pretense of getting water.

Aizawa’s probably dehydrated. His diet is still questionable at best, and Shinsou heads back to the living room with his arms full of water bottles and power bars. He finds Aizawa sitting on the floor, sleeping bag draped over his shoulders, poking at his laptop.

Shinsou drops everything on the floor, letting the water and snacks join Aizawa’s mess of clothes and papers and—are those printouts of their emails?

“Your work schedule is too busy,” Aizawa says by way of greeting. “You’re never going to have a healthy sleep schedule this way.”

Shinsou blinks at him dumbly. “I brought you... fifteen bottles of water, I think. You're probably dehydrated.”

Aizawa sighs. “I hung up before I could bitch out your agency. I hate rut hormones; they always make me act... Well. You should still adjust your schedule, though.”

And then it clicks. Shinsou is stupid for thinking they’d have some absurd dominance show-off. Instead, his protective instincts are off the charts. He wants to spend the next five years brushing Aizawa’s hair, wrapping him up in his sleeping bag and holding him and—

“I’ll take a look later,” Shinsou says, sitting behind Aizawa and draping his arms over his shoulders. It’s getting dark out, and the light from the kitchen is too dim to do more than cast fuzzy shadows in the living room. “Let’s go to bed. I’ll carry your stuff.”

Aizawa looks up at him. “I’m not an omega, Shinsou. You don’t need to baby me.”

Cool, cool. It’s not really rejection, but Shinsou feels rejected anyway. He grabs an armful of their crap and heads to the bedroom, hoping Aizawa will follow on his own.

breaking the thread rq to link to @/shiru_desu's beautiful drawing of the couch scene! they look so damn gorgeous in this, thank you so much!

https://twitter.com/shiru_desu/status/1312145587853172736?s=19

https://twitter.com/shiru_desu/status/1312145587853172736?s=19

Aizawa follows. Of course he does, naked except a pair of old black underwear and the sleeping bag slung over his shoulder. He looks grumpy. Shinsou suddenly wonders if he’s already overstepped Aizawa’s boundaries.

According to their emails, he hasn’t. But… maybe he’d pushed too hard on this whole thing. Maybe Aizawa isn’t comfortable with their shifting relationship, and he really doesn’t seem as painfully eager as Shinsou is for more.

“I didn’t mean to make you uncomfortable,” Shinsou says. Aizawa frowns. Shinsou cracks a window because it feels hot. Too hot, too much of Aizawa’s scent and he’s starting to feel it in his mind, crowding out his thoughts and replacing them with things like /mate/ and /protect/.

“You didn’t.” Aizawa’s voice is quiet. Shinsou looks out across the rooftops of the neighborhood, and wonders if locking himself in a small apartment with his former teacher really /was/ his brightest idea.

“You seem uncomfortable,” Shinsou says. “Or reluctant.”

He finally turns around, only to see Aizawa on his bed, legs in his sleeping bag, juice pack halfway to his mouth. He looks… completely at ease. And vaguely guilty?

“I’m not, I—” Aizawa cuts himself off, scrubbing his face. “I don’t really know how to act.”

Shinsou is stunned. He’s seen Aizawa be emotionally vulnerable maybe two or three times in his life, and only for momentous occasions.

When he’d said he was proud of Shinsou at graduation. A handful of times protecting his students, when the raw fear and determination on

his face was unmistakable. Once when they were working together underground, and he’d thought he’d been blinded. Shinsou had held his trembling body for hours until the blinding Quirk had worn off.

But vulnerable just for the sake of Shinsou’s questioning?

That had never happened. It doesn’t matter how many emails they send. Sex is shifting things between them, in a way that leaves Shinsou hopelessly intrigued.

“I don't either,” Shinsou offers. Aizawa scoffs.

“No, you’re just being incredibly awkward. I’m trying not to be, not to be. Look, you know I’m not an aggressive alpha. That doesn’t mean I don’t have any of the traits,” Aizawa continues, setting the juice pack down as he meets Shinsou's eyes.

Suddenly, the few feet of space between them seems far too small. Shinsou feels like /prey/, even though he’s supposed to be the hunter, not the hunted.

“What do you mean?” he asks.

“I’m not aggressive,” Aizawa says, staring him down, “but I’m very, very… possessive.”

Shinsou swallows hard, remembering their emails. Marking. Alpha on alpha marks don’t last any longer than it takes the bite to heal, and—Aizawa snaps his teeth.

“You’re possessive of me?” Shinsou asks, unable to hide his surprise. Aizawa rarely shows enthusiasm for anything.

Even earlier, coming on Shinsou’s couch, he’d been painfully controlled.

“I don’t like it when I can’t control myself,” Aizawa says, once again astounding Shinsou with his honesty. “You make it… hard to resist.”

“Don’t resist, then,” Shinsou says, crossing his arms. “You know what I’m comfortable with.” In those godforsaken emails.

Aizawa’s lip twitches. He slides out of the sleeping bag, sitting on the edge of the bed. He raises a hand, limply gesturing for Shinsou to come over.

“Big talk from the big alpha,” Aizawa says. “If it’s so easy, then come here and let me mark you.”

Shinsou obeys, coming to a stop between his legs. His blood is singing, either from the idea of Aizawa's teeth in his neck or from his commanding, grating tone. Probably both.

“On your knees,” Aizawa says, smiling slightly. Shinsou glares at him.

“Is that necessary?”

“Do it.”

Shinsou bites back his retort, because he’s supposed to be behaving himself. He drops so fast his knees crack against the hardwood.

Aizawa stares down at him, and Shinsou is suddenly reminded of his well-known sadistic side.

“Well?” Shinsou chokes out, rigid at the way Aizawa leans over him, elbows on his knees, suddenly looking amused. Aizawa reaches out a hand and pats his cheek condescendingly.

“Good alpha,” he says. “Bare your neck for me.”

“Are you trying to make this harder?” Shinsou growls.
Aizawa’s hand drifts under his chin, nudging it up. Shinsou’s throat feels vulnerable, defenseless under Aizawa’s dark eyes.

“I’m trying,” Aizawa says, “to make this /fun/.”

“For who?”

“Me,” Aizawa says, leaning in. Shinsou can hear his pulse singing in his ears, and he’s nearly shaking with effort just to stay on his knees. Aizawa was right. Aizawa is always right, and /fuck/ it’s hard to let this happen.

But he does. Because Shinsou’s not an animal. And even if Aizawa’s stubble scratching at his throat has his hackles raised, he holds still. Aizawa mouths at his neck, pressing open-mouthed kisses over sensitive scent glands.

“Just do it,” Shinsou hisses. He feels about five seconds away from grabbing Aizawa’s hair and yanking him down to a more acceptable level. Dick-level, maybe.

“I’ll get to it,” Aizawa murmurs into his neck. “Eventually.”

“What.”

“It’s just practical, Shinsou,” Aizawa says, too-loud just beneath his ear. “Can’t have you going all aggro-alpha in the middle of things. It makes sense to find out your limits now.”

“You just want to mess with me.”

He almost regrets saying it, because Aizawa reaches down, takes his dick in hand, and squeezes. Shinsou honest-to-god whimpers.

He’s still riding the embarrassment of it when Aizawa says, “Yeah, maybe. Turns out you’re fun to mess with.”

Shinsou presses his lips together, trying to bite back fighting words. Instead, he focuses on Aizawa’s breath hot on his neck, the way he’s working his dick into full hardness. It feels good.

Shinsou knows it feels good, and it’s not even that far from anything he’d do during normal sex.

But it’s not normal. And Aizawa told him to go on his knees, and he’d obeyed. Like a dog. He’s trying /stay/ obedient. His chest feels tight, breath coming out in little whines.

“Good boy,” Aizawa croons, “doing so good for me.”

“Eat shit,” Shinsou says, because the alternative is launching off his knees and tackling Aizawa onto the bed. Aizawa pulls back, looking at him.

“Such a rude boy.” He’s acting unimpressed, disinterested, and even if it’s obviously a charade, it gets under Shinsou’s skin. Aizawa’s head tilts, black hair falling across his face like a shadow. “Say sorry, Shinsou.”

Shinsou is trembling in place, feeling the way Aizawa’s hand slides to his throat, fingers digging into the side of his vulnerable neck. And fuck, Aizawa knows how he feels about his neck. He’s going for the throat on purpose, because he’s testing Shinsou.

Shinsou’s in control of himself, but only barely. His hold on his instincts is razor thin, his teeth ache with the urge to bite back. He can’t stop thinking about how /good/ Aizawa had felt under him, groaning around his knot. He could make it happen again.

Just needs to grab Aizawa’s hand, unbalancing him with a pull. He put him in his place, and—no. No.

“You’re a dick,” Shinsou grits out. Aizawa runs his hand slowly up the length of Shinsou’s cock, thumb trailing over the head, his dark eyes on trained on Shinsou's face.

“So goddamn rude,” Aizawa says, his hold tightening on Shinsou’s throat and cock simultaneously. Shinsou bites back a groan, letting Aizawa tug his face closer by the neck. “Come on, say sorry to your alpha,” he murmurs. “I know you want to be good.”

“You think,” Shinsou huffs out, “that you can make me into some… into your…”

“Into my little obedient bitch,” Aizawa finishes for him. “Yes, I do.”

Shinsou flinches, spine going straight. The urge to retaliate is inevitable, a shark swimming in his blood.

It’s a testament to his desire to please Aizawa that he manages to stay on his knees, but there’s more than one way to have power.

Shinsou knows all about taking control without being physical.

“Good,” Shinsou snarls. “You want to talk about /good/? Why don’t you tell me how long you’ve wanted to fuck your /student/?”

Aizawa goes deathly quiet for a moment. Then he grins abruptly, horrifyingly. "About a week. How long have you wanted to fuck your teacher?"

Yeah, Shinsou had miscalculated. He's flushing red, unable to express that even his first wet dreams had been about Eraserhead, even if he is literally achieving those dreams as they speak. Then Aizawa's grin fades to a faint smile, and his hands drop from Shinsou's body.

"You don't have to answer, kid. I already know."

"Oh no, oh my god," Shinsou groans, dropping down to sit on the floor. This is becoming mortifying.

"You weren't exactly subtle," Aizawa says. His tone is perfectly practical, but Shinsou is still dying of humiliation. "I've been teaching for over a decade. Student crushes are something you get used to deflecting."

"What changed, then?" Shinsou manages to ask.

"I don't know, ten years? And my arguably attractive colleague unexpectedly throwing himself at me when I am particularly… persuadable.”

Colleague? Aizawa sees them as equals, which Shinsou supposes should be obvious, given what they're doing.

Still, it leaves him feeling warm, mortification fading as quickly as it had come. Shinsou scoots forward, resting his elbows on Aizawa’s knees to look up into his face. Dark hair tickles his cheeks.

“It’s not every day a hot, young alpha drops right into my lap,” Aizawa adds, that faint smile still on his lips. “Can you really expect me to turn that down?”

It’s clearly meant as a compliment, but it still rubs Shinsou the wrong way.

Aizawa, regularly picking up hot, young alphas? Is Shinsou just another one? Why had Shinsou never heard about this part of his life? Aizawa /had/ said he wasn’t his first alpha. Maybe… maybe this is a thing for Aizawa. That he likes. Shinsou isn’t sure why that bothers him.

“You get a lot of hot, young alphas then?” Shinsou asks, blinking slowly. Aizawa’s smile suddenly shows teeth.

“As you love saying, I’m 42. I’ve been around the block.”

Shinsou doesn’t expect to feel his relative inexperience so acutely.

Aizawa /is/ his first alpha, and he suddenly feels nerves. Not the warm, sparkling kind he’d had before Aizawa showed up. These feel like they’re eating away at his stomach lining. He almost feels sick with it.

Shinsou looks down, noting a hole in Aizawa’s underwear. He can see a few hairs poking out. Why does he have to be so hopelessly attracted to him? Why does he feel so /much?/

There’s a low hum above him, then suddenly there’s fingers on his chin, firmly tilting his face up.

Aizawa is staring down at him, eyes black as night.

“That’s not why I’m here, though,” he says slowly. Shinsou is speechless. Aizawa breathes out a small, self-effacing laugh. “I keep forgetting you’re not used to me teasing you like this. This is new for me too, you know.”

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