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Katsuki stopped growing at the most insulting fucking height his body could have chosen. He had been fine with his height in the metric system. 182 centimeters. That’s respectable. Formidable, even. Then one day Pony just had to open her stupid goddamn mouth and say “182 centimeters? That’s about 5’11, right? Almost 6 feet!”
“Almost.” Like he was missing some milestone, some stretch goal.
Fucking Americans and their stupid fucking units of measurement. To add insult to injury, she had been wrong. 182 centimeters was closer to 5’10.
Of course, being the person he was, he’d let that fester inside him.
So, when he had realized very soon afterward that he had to tilt his head ever so slightly upwards to speak to Izuku, he had promptly interrupted their conversation to explode his own pencil case and storm off. He then refused to speak to Deku for a full week, for both of their sanities.
______
He's mostly come to terms with the height thing now that they've graduated. They're coworkers at Miruko's upstart agency, and often pair up for hero work, so Katsuki kind of has to be civil if he wants to get shit done.
He glares at the coffeemaker, willing it to work faster so he can finish his paperwork for the night. He and Deku take turns writing the patrol reports when they pair up. It’s Katsuki’s turn today, but all he wants at the moment is to go home, take a bath, and jack off. These are not unreasonable desires, he’s a simple man.
His train of thought is disrupted when a wall of warmth approaches his back, and a deep voice breathes out an “excuse me”. He stiffens as Izuku’s arm reaches over him to grab something out of the cabinet above his head.
Izuku’s other hand comes to rest lightly on his shoulder. His brain stalls out for a moment, focusing only on the heat, the feeling of being trapped against the counter, on how big Izuku is now. Okay, so Katsuki isn't really "over" the height thing. Mostly, he just understands that he really wants to be under Izuku now.
Everything about Deku as an adult is designed to torment Katsuki. His voice has deepened, but still retains Deku’s breathy speech patterns, a combination that is ultimately more sexual than it has any right to be. He’s big as hell, nearing All Might or Endeavor proportions, and he's so much more confident now.
So when he does shit like this, without even realizing what he’s doing to Katsuki, it drives him absolutely batshit. Izuku could be fucking him like this, up against the counter. It isn’t like Miruko would give a fuck. Hell, she’d probably just break out the popcorn. Katsuki tenses further, using every ounce of control he has to resist grinding his ass back into Deku’s stupid fucking dick.
A moment later his restraint is rewarded by a pat on the shoulder and a “thanks” as Izuku retreats with a box of crackers that had supposedly been his goal. Katsuki frowns as he watches his childhood friend turned wet dream retreat. Izuku doesn’t even like those crackers.
______
That’s the first hint. Those crackers Izuku doesn’t even like.
The next comes when Katsuki is in the agency gym three days later, wrapping up his post-shift workout. It’s a Thursday, which means he gets the morning to afternoon shift, while Deku gets afternoon to evening. He had seen Deku enter through the glass walls of the gym while he was on the treadmill, but Katsuki had thought Deku’s wave and his acknowledging head tilt would be the extent of their interaction for the day.
As luck would have it, though, the menace just so happens to circle back during Katsuki’s cooldown, interrupting his stretches with a “wow, Kacchan is so flexible!”
Katsuki freezes where he’s stretched in half touching his toes. He slowly lifts from the stretch to level his narrow-eyed gaze at Deku, who’s fully outfitted in his hero costume and is clearly interrupting his path out towards patrol to harass Katsuki.
Deku just barrels on, ignoring the look Katsuki is giving him. “Can you do the splits?” He asks, the picture of innocence.
“Of course I can,” Katsuki scoffs. Stretching is important, so he does it every day after his workouts, but he usually saves the more intense stuff for when he’s alone. He doesn't want extras oggling him more than necessary.
“Wow, Kacchan, can I see?”
Katsuki narrows his eyes at the nerd again, but all he gets in return is another innocent look.
Katsuki scoffs, going back to his stretches. “Fuck off.”
“It’s okay if you can’t do it,” Deku says earnestly, “you didn’t have to lie, I just thought you might be able to.”
Katsuki narrows his eyes at Deku. He’s fairly certain the asshole is trying to goad him into doing the splits, but just because he knows what’s happening doesn’t make it any less effective. “I will do the fucking splits to prove that I can, then you will fuck off to your patrols and leave me alone.”
“I don’t have patrol for another--” Deku checks his watch “--fifteen minutes, but sure!”
Katsuki stands up facing Deku, turns sideways, and sinks into a split. It’s been a week or two since he last did a full split since he’s mostly been working out at the agency gym, so it burns a little, but he’s able to do it with no real problem. He twists his torso to look at Deku. “Fucking see.”
“Wow! Can you touch your toes like this?” Before Katsuki can respond, Deku’s touching him, running his large calloused hand up Katsuki’s side, lighting his nerves up as he gently guides his arm up, then pushes him into a bend with a second hand at his back. Katsuki follows silently, sensing that if he tries to protest he won’t be able to make it convincing.
The muscles in his arms and legs burn just a bit with exertion, but he touches his toes easily, and the hands leave his body.
“Wow, that’s so impressive!” Deku exclaims as Katsuki lifts himself to sitting, then out of the splits. “I could probably put you in a full Nelson, with legs and all, and it wouldn’t even hurt you!”
Katsuki almost chokes on his spit in surprise as he pictures that. He might be bugging, but he’s pretty fucking certain that’s a sex position. “The fuck?”
“You know, like the wrestling hold?”
Katsuki doesn’t think he’s ever seen a wrestler do a full nelson, legs in-fucking-cluded, but he’s not willing to bring up the concept of sex when he’s already starting to get a bit turned on. The shorts he’s currently wearing would not fucking hide much.
“Yeah, sure.” Katsuki says, dropping into a front stretch to distract himself from horny trains of thought. “Weren’t you going to leave me the fuck alone after I did a split?”
“Sure, Kacchan,” Deku agrees. His hand rests on Katsuki’s shoulder, then runs along his arm for a moment, leaving gooseflesh in its wake. “See yah.”
——-
The first thing Katsuki does when he gets home that night is google “full nelson”. There are no images of the position being used with legs. So he tries googling “full nelson with legs”. There’s nothing with anyone pinning someone else's legs. Tentatively, he googles “full nelson sex”.
“It’s a sex position!” He exclaims, gesturing incredulously at his laptop. “That is fully just a sex position!”
He crosses his arms, fuming at his results. Deku had played all innocent, but the inclusion of the legs in the hold is fully just an adaptation as a fucking sex thing, there’s no way he didn’t know that.
Sure, yeah, he could hold that position just fine, and Deku could definitely put and keep him in it. Shit, he could probably even do it standing up. Maybe even in front of a mirror...
Katsuki tilts his head, still looking at the results, but now picturing himself and Deku in that position. Okay. That’s actually a pretty fucking hot image. He’s definitely going to have to jack off to that later.
He shakes his head, clearing his thoughts. For now, though, he’s indignant. Deku absolutely is fucking with him. He’s up to something. Katsuki’s sure of it.
_____
After that, he’s on his guard, keeping an eye out for any more weird-ass behavior. The final straw comes in the agency locker room.
Katsuki’s shift just ended, and he had had a pretty rough fight with a villain during. He’s looking at his bare torso in the mirror, twisting to get a better view of a large mottled bruise there, when a familiar, scarred hand gently brushes against his tender side. His skin breaks out in goosebumps, and he shivers at the unexpected touch.
“That’s a nasty bruise you’ve got there,” Izuku says, sliding up closer behind Katsuki. “Do you want me to get you an ice pack?”
Katsuki bats his hand away. “No. Fuck off.”
Instead, Izuku steps just a bit closer, resting his chin on top of Katsuki’s head and slotting his front to Katsuki’s back.
“Wow, I didn’t realize how much of a size difference we have now.” Izuku presses his hands over Katsuki’s waist. “Your waist is so tiny, too.” Izuku grins cheekily. “We should go ice skating sometime, bet I could lift you.” Deku’s fingers trail across his stomach as he repositions his hands to Katsuki’s side, then mimes a lift.
Katsuki shivers at the light contact, the muscles in his stomach jumping. His face heats a bit, and he slaps Izuku’s hands away again, making eye contact with him in the mirror. That’s it.
“Just fucking say it already, Deku. Are you trying to emasculate me, or trying to fucking fuck me?”
Izuku blinks owlishly back at him in the mirror, a blush dusting his cheeks. He steps back, his hand coming up to rub the back of his neck sheepishly. “Sorry, I didn’t think there’d be any confusion on that, I guess I did tease a little too much.”
Katsuki rolls his eyes. “What the fuck ever.” He stomps over to the bench and grabs a shirt to throw on, then tosses his duffel over his shoulder. Deku watches silently.
“Well?” Katsuki raises an eyebrow. “Are you coming to my place or not? It’s been a long fucking day.”
Izuku brightens at that. “Sure,” he chirps, “sounds good!”
____
They don’t talk much when they get to Katsuki’s place, too busy putting their hands and lips all over each other’s bodies. But Katsuki always seems to get talkative when someone has their mouth on his dick, and he can’t resist the urge to bring up Deku’s shitty seduction methods.
“You’re so fucking unsubtle,” Katsuki pants, grinding his dick up into Deku’s mouth, “A full nelson with legs? Fucking please.”
Deku pulls off his dick with a wet pop, grinning as he wiggles the three fingers in Katsuki’s ass. “Wanna try it?”
Katsuki stares at him for a moment, then huffs a laugh. “Yeah, let's fucking do it in front of the mirror.”
Izuku slips his fingers out of Katsuki’s ass and lifts him up, carrying him over to the mirror, then adjusting his grip to lift Katsuki’s legs until he’s bent in half, Deku’s forearms supporting his weight by the crook of his knees, his hands linked behind Katsuki’s neck. In the mirror, he can see the crackle of green electricity as Deku activates his quirk. He feels a jolt of electric arousal straight to his belly at the sight.
Izuku’s voice comes out in a hot puff of air by Katsuki’s neck, sending a shudder down his body. “You ready?”
Katsuki nods, breathing out a shuddery “yeah”. Deku’s hands are occupied, so Katsuki reaches behind himself to grab Deku’s cock and position it at his entrance.
Izuku’s hands gently press Katsuki’s neck down, giving him a full view of his cock bobbing in the air as Deku slides him down. His thighs burn, adding a layer of sensation to the already overwhelming feeling of being stuffed full by Izuku’s very fucking proportionally sized dick. They’re both slick with lube and spit from foreplay, and Katsuki can feel the soft hum of Deku’s quirk where their skin is pressed together. It’s oddly relaxing, and Izuku’s cock slides in easily.
“Does it hurt?”
Katsuki bristles at the coddling. “Just shut up and fuck me.”
The buzz of Deku’s quirk intensifies, and Katsuki’s eyes widen as Deku begins bouncing Katsuki up and down on his dick. Deku’s impressive girth and the position have his dick grinding against Katsuki’s prostate with every thrust. His stomach feels warm and fluttery with pleasure, and his cock aches to be touched, to the point where even just the sensation of the air moving around it as he’s fucked is enough to have his nerves lighting up.
Katsuki awkwardly tries to maneuver his hand to his lap to get himself off, but just as he’s about to touch himself, his hand is yanked back. He nearly sobs in frustration, letting out a choked noise of displeasure mixed in with his moans. “Wha--what the fuck, Deku?”
Black whip restrains Katsuki’s arms, holding them in place along his thighs. Katsuki can barely move like this. He raises his head a bit to make eye contact with Deku in the mirror, doing his best to glare and will away the redness in his face.
Deku just smiles, his voice barely winded. “You were rude! Rude Kacchan doesn’t get to touch himself.”
Then Deku increases the pressure of his hands against the back of Katsuki’s neck, pushing his head down to watch himself get fucked again. Katsuki flexes his biceps to test the hold, twisting his upper torso indignantly. “Fuck you, you fuck, let me touch my dick!”
Deku’s thrusts slow a bit in response, but don’t stop. “You remember the safeword?”
“Yes, I remember the fucking safeword!” Katsuki wants to touch his dick, but using the safeword would mean Deku would stop altogether, and he’s not fucking having that. Besides, there’s something… weirdly nice about being held in place, struggling against the restraints just to feel them holding fast.
Deku sighs. “You’re so loud, it’s hurting my ears. If you’re just going to complain even if you like something, I’m going to gag you.” A new tendril of black whip creeps between Katsuki’s lips, emulating a bar gag and holding Katsuki’s tongue in place against the floor of his mouth.
Katsuki tries to let out a sound of indignant protest at that, but the head of Izuku’s cock scrapes against his prostate and it comes out more moan than anything.
“Make sparks with your palm if you need me to take the gag out.”
Katsuki’s sick and fucking tired of being babied while he’s trying to get his brains fucked out. He turns his head and bites down hard on Izuku’s forearm. “Fuck!” Izuku yelps, evidently startled enough that he loses his grip on Katsuki a bit. As a result, Katsuki’s ass slams down on Izuku’s thighs, and Izuku’s cock buries itself so deep and hard into Katsuki that he sees stars, his cock jolting against empty air.
A moan punches out of him, and he’s sure he’s drooling, but he doesn’t even care anymore, with how close he’s teetering to the edge.
He grinds his ass in little circles against Izuku’s cock, the rim of his asshole dancing with nerves and a deep pressure building inside his belly.
“Oh my god.” Izuku finally sounds out of breath now, stumbling back to sit in Katsuki’s desk chair. “You took it all.”
Katsuki wasn’t even fucking aware Izuku had been holding back, the angle that he had been seeing in the mirror apparently obscured that fact from him, but he wants it all now. He grinds more insistently, moaning in protest to try to get Izuku to start fucking him again.
“Okay, okay,” Izuku says, leaning back in the chair and readjusting to grip Katsuki with a hand on either asscheek.
Katsuki tosses his head back against Izuku’s shoulder and moans as Izuku starts fucking him again, now with the added sensation of his big hands spreading Katsuki’s ass wide open. One finger comes to toy with the rim of Katsuki’s asshole; and he whimpers, drool sliding uncontrollably down his cheek around the gag.
“Fuck Kacchan, you look so pretty like this,” Izuku breathes. “So gorgeous, Katsuki.” Then Izuku slides his finger into Katsuki’s asshole along with his dick, and Katsuki’s done. He moans like a goddamn whore, his stomach spasming violently as he comes in messy spurts all over himself and the floor.
“Oh my god,” Izuku moans, “oh my god, that was so hot.”
Suddenly he’s fucking Katsuki even harder, carrying him through his orgasm and to the point of almost painful pleasure before finally dropping Katsuki in his lap and grinding into him, riding out his own orgasm.
For a moment, they’re both still, just panting for breath, then black whip gently begins to recede, lowering Katsuki’s legs to the ground. They’re stiff from the sustained position, but he focuses on the pleasant warmth of Deku’s cock inside him instead, stretching his arms over his head. “Fuck, that was good.”
Deku makes an exhausted noise of agreement, and Katsuki grins, turning back around to face him. “Guess that means we’ll have to do it again.”
Izuku smiles at that, giving a huff of laughter. “Guess so.”