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Katsuki ends up in Denki’s dorm a lot. It's not his fucking fault though, it's his last resort. He doesn't want to hear Eijirou get his back blown out by shitty Deku. His first choice would be Hanta, but that fucker is always hanging out with Icyhot. Like hell he's going to step foot into Mina’s room and risk her forcing him into a 'girl's night.'
Denki’s the only option. The alpha is a social butterfly, half the time he's not in the room. Katsuki will hang out while waiting for the idiots so he can go back to his room. Sometimes Denki never shows up, but the times he does, he'll sit at his desk bemoaning all the homework he's let pile up. He tries to get Katsuki to help. He doesn't. Usually. Other times, Denki plops onto the floor and plays on his switch. It's not terrible. When no one else is around, Denki chills put, like he no longer needs to put on a funny act for everyone. At first, it bothered him that he didn't think Katsuki was worth the effort. After the first couple times, he realized Denki was actually relaxed and comfortable with him. It made him feel nice. Maybe a little special, but fuck if he'd admit it out loud that it made his chest warm.
It's one of the evenings that Denki isn't there that Sero pops in. "Oh! Bakubro! Whatcha doin?"
"Saving my ears," he mutters as he gets comfortable on the bed. "The fuck you doing in here?"
"Gotta borrow Denki’s English book!" He grins and rifles around the desk.
Katsuki grunts a response and picks at the blankets.
"Are you making a nest?"
He freezes. "No."
Sero tilts his head to the side. "You sure? That looks like a nest."
"Yes I sure," he hisses. "His bed is shit, I gotta make sure the lumps are smoothed out and there's not fucking food hidden in here."
"Dude. I'm a beta, but I know a nest when I see one."
He casts an angry glance around the bed. Fuck. He's been making nests. He doesn't hardly even nest in his own fucking bed, and he's doing it in Denki’s? Embarrassment flares through him, heat creeping into his cheeks.
"Um, I'm gonna go. Good luck with your nest."
Katsuki glares at the now obvious nest, pissed that he never realized what he was doing. The door clicks shut after Sero’s departure, and he considers dismantling it. Anxiety swells in his chest at the idea of dismantling the source of comfort.
As much as he hates to admit it, the times he's been stressed or upset and felt the urge to seek Denki’s room out made sense now. He doesn't nest in his room because it's in here and it's why he gets frustrated every time he has to re do it after not coming over for a few days.
Denki has to know.
Katsuki glances around the walls of the nest, a newfound itch to fix parts of it under his skin. To make it the best now that he knows he's doing it.
What if Denki doesn't know because his other nests have been shit?
A tiny little whine leaks out his throat at the thought. Nope. Fuck that. He's not letting irrational instincts make him second guess himself.
He flops onto his back and unlocks his phone to distract himself. His scent as lost most of the anxious tinge when the door opens and Denki waltz in. Katsuki knows he picks up the smell. Denki’s nose flares a little and furrows his eyebrows. He bites his bottom lip in concern, having some kind of internal battle before sliding down onto the floor. He sits where he always does, toward the head of the bed where he can easily reach into the table for the switch.
Then he just, acts normal. Tells Katsuki about whatever stupid shit he did that day and he pretends not to listen like he always does. While part of himself is relieved because he doesn't have to confront the elephant in the room, he's also going crazy. Not because he's been doing something without knowing (it does bother him though), but because he wants to know what Denki thinks about the nest. It's stupid and he's mortified that he even needs approval of it. It takes him too long to catch the sour notes of his own scent.
"Are you okay?" Denki asks tentatively, probably scarred by past attempts and receiving explosions to the face.
He opens his mouth to bark out a 'I'm fine,' but instead blurts out, "Do you like my nests?"
"Dude! I love your nests!" Denki grins up at him.
"So you've know the whole time?" He mutters, wishing he could be swallowed by the bed.
"I mean, yeah. I'm pretty dumb, but I'd notice an omega nesting in bed."
"Why did you say anything?" He snaps.
"I didn't think I needed to." Denki shrugs. "You never acted like you needed some kind of approval, and I didn't want to embarrass you and make you not want to do it anymore."
"I didn't even know I was doing it," he huffed.
Amusement dances in his eyes. "Really? I'm not gonna lie, I think it's pretty cool."
"What? It's stupid."
"No, man!" He scrambles up to his knees to get a better look at Katsuki. "It's awesome you picked my bed to nest without actively thinking about it! It's like, the biggest compliment."
Katsuki looks away, unable to keep staring at Denki’s excitement when his face is red like a tomato. "So it doesn't bother you?"
"What? No! I get the best sleep after you do it. And it's like, super comforting and calming if I'm having a rough day. You smell really nice!"
Katsuki preens a little at the statement, likes that Denki feels that way about the nests he makes. He brings himself to look back at him.
"Why don't you ever get in them when I'm here then?"
It's Denki’s turn to blush. "I'm not just gonna ask to get into your nest."
"It's your bed!"
"It's your nest!" He protests.
"You don't have to have permission to sit on your own bed," he rolls his eyes. "Doesn't matter if I've fucked with the blankets."
"Kacchan," he whispers, eyes comically wide. "Are you inviting me in?"
He ignores the pounding between his ears. "It's not that deep."
Denki nods frantically. "It is! Would you want Sero or Mina to just get in?"
He scowls, annoyed at the suggestion. "Of course, not! Like I'd want those idiots in my nest."
"See!" He leans forward, careful not to touch the carefully crafted wall. "Are you asking me in?"
Katsuki’s throat tightens and wishes the heaviness of the question isn't as suffocating as it was, that he could answer without it meaning anything. It does, and he kinda wants to bolt to avoid the gravity of it, but also needs Denki to properly scent it now.
"Yeah," he rasps.
Denki freaks out a little, he's never been invited into a personal nest before. Sure, lots of his classmates have let him in groups nests, but that's not the same.
They weren't Katsuki. The super cute guy he's been crushing on since first year. Who's been nesting in his bed. For months. He's not super surprised he didn't realize he was doing it, he's a little dense in the emotions department.
He's lucky he's strong and a great hero.
Katsuki’s stare is open and vulnerable, and Denki heart misses a couple beats. He doesn't know what he did, but he needs to figure it out to make sure he never stops so he never loses this.
He climbs over meticulously to not mess anything up and settles in close to Katsuki with the limited amount of space. The sharp edge to his scent is back, but Denki understands it now.
"It's a great nest, Kacchan."
Pleased omega pheromones fill the air to match the darker shade of red on Katsuki’s cheeks and ears. Denki wants to hoard it, to make sure he can always spell it on his sheets. Always wants to ensure he's happy and secure when he's with Denki.
"Can you?" Katsuki clears his throat . "Fuck, will just scent it?" He glares at him, but it's soft and hesitant and Denki would probably do literally anything if given the look.
He picks a few spots by the top to swipe his wrists across, and releases more pheromones. Denki really tries not give too much stock into his alpha instincts, he's Denki first, but agrees with them preening at Katsuki visibly relaxing. He did that, his scent and nesting materials are helping create a safe spot for him to curl up and get comfortable. Katsuki tucks a lose blanket under his chin, one that Denki just scented, and cues up his phone screen. Okay. Denki can just chill with him. Totally cool. He definitely can distract himself with his own feed and games when there's an adorable omega inhaling his scent. In the nest they were both in, that now has a pleasant mixture of their pheromones.
And it works. Sort of. He successfully keeps himself from blatantly staring in awe, but he frequently peeks over at him. They hang out tons, and Denki manages to be normal. He scoots closer, enough to brush their arms together while playing on their phones, maybe he'll be able to focus a little better with some physical contact.
When Katsuki leans into it, Denki almost sort circuits. He hasn't even recovered from that when the purring starts. He's never hear it. Katsuki’s purring, and it turns his insides to mush.
He's doing his best, prides himself on being respectful and conscious of boundaries, but all of it is overwhelming. The smell of omega, and the intimacy of the nest, and Katsuki purring for him.
Denki’s a weak, horny man.
He struggles to conceal the smell of his arousal, doesn't want to make Katsuki uncomfortable.
"Oi."
Denki squeaks, dropping his phone on his nose. One look at the slightly dilated pupils, and he knows he knows.
"I'm sorry! I can leave!"
"Do you want to leave?"
"No! I want to stay! Ikindaalsowanttokissyou," he rushes out.
Katsuki’s eyes widen and the pretty flush spreads down his neck. "Okay."
Holy shit. He's gonna do it, he's getting the chance of his dreams here. He shifts onto his side, gently turning Katsuki by his waist. Once they are facing each other, Denki brushes his knuckles along his jaw. Katsuki parts his mouth and softly inhales.
Kissing Katsuki isnt an all consuming need to devour him, he's not desperate and clacking their teeth together, but it's still amazing and addictive. His lips are slightly dry, but are pliant and eager to follow Denki’s lead. He swallows the faint gasps and quiet moans, riding one of the greatest highs he's ever experienced. Trailing his fingertips down the side of his neck, he gently kneads the skin around the gland. Katsuki groans, reaching out to fist the front of his shirt to pull him closer. Encouraged by the gesture, Denki adds pressure to the kiss and traces his tongue along his bottom lip. He continues massaging with his thumb while licking into Katsuki’s offered mouth. Time gets muddled for Denki, he knows he pauses for air a few times, but beyond that he's not sure how long they make out for. It's the sweet scent of slick when Katsuki shifts a knee between his legs that crashes him back to reality.
Wrenching his face away, he grips his thigh. "Ookay, we gotta stop now."
There's splotches across Katsuki’s cheeks, and almost no red left from dilated pupils. "Why? Do you not want to?" He raises an eyebrow glances down at his crotch where he know his boner is tenting his sweatpants.
"That's the point!"
He nudges Katsuki’s leg away, sending another waft of slick to his nose, and Denki sucks in a sharp breath. "I wanna do more stuff with you. So much, and that's the problem," he whines.
"Then... why don't you?"
"I don't want you thinking expect something from you!" He groans. "I don't think I'm owed sex just because you invited me into your nest."
His face scrunches up in confusion. "I know that, moron. I'm horny as shit and I wouldn't do this with anyone but you."
He shouldn't share things like that, it's going straight to his ego. And dick. "Have you even had sex?"
"No, but I know how it works." Katsuki scowls at him.
"How about we stay over the clothes," he suggests.
"You want to cum in your pants?"
Denki scrubs a hand over his face. "Not really, but if I see your pussy, I'm gonna want to put my dick in it."
The smell of slick thickens, and Katsuki nods, voice rough. "Okay, yeah, we can do that."
"Are you agreeing to my idea or being super unhelpful?"
He opens and closes his mouth a couple times, ending with a pout. (It should be illegal how cute that is.) "We can do it your way."
His dick throbs at the implication that Katsuki would let him, that Denki could sink inside him right now. Nope. One of them had to be responsible.
"Okay, so like, if I grind against any part of you, I'm gonna last for like, two seconds. So you should cum first."
They lay there for a few awkward seconds, Katsuki's faced getting redder and redder until he clears his throat.
"Well? Are you gonna do something?"
"D... do you want me to do it?"
"I mean, yeah! Did you want to just watch me get myself off?"
"That would be hot."
"No! I don't.. that's weird. I'm not doing that."
Denki nods, tracing his fingers along Katsuki's waistband. "I can do it. Ill make you feel good."
Katsuki hykes his leg up to rest of Denki’s thigh, and he takes it as an invitation to slip his hand down the front of his pants. Even through the panties - he'll process that tidbit later - there's so much heat coming off his cunt. He presses his palm into his clit and strokes his fingers over the wet fabric with as mush pressure as he can.
Katsuki whimpers and tucks his face into the crook of his neck. The damp breath on his scent gland sends a thrill down his spine, and he grinds the heel of his hand firmer in a circular motion. Katsuki’s hips are bucking into his hand, and he shallowly thrusts two fingers inside. It's not a lot with the barrier, but elicits a moan. He replaces his palm with his thumb and kneads it over his clit, sticking with what seems to get the most reactions. The panties are soaked, and his fingers keep losing purchase with the way Katsuki twitches and grinds against him in search of more friction.
It's an accident when one finger sinks inside his cunt, but it makes Katsuki keen lewdly by his ear and Denki thrusts it in and out while rubbing his clit. Katsuki tenses, thighs shaking uncontrollably, and cums with a loud moan. As soon as the orgasm ends and he slumps. Denki rolls him onto his back and rolls his clothed erection into this cunt in an imitation of fucking him. Katsuki whines from sensitivity, but bucks up to meet him. Denki pins their threaded fingers to the bed above his head presses his forehead to his. Hazy, beautiful eyes lock with his as he ruts between Katsuki’s legs. It doesn't take long when he can feel the pulsing heat through layers of pants and has been hard for so long. When the pressure in his stomach explodes, he buries his face into Katsuki’s shoulder.
It's always gross cumming in his own underwear, but it's totally worth it this time when his body is lined up with Katsuki’s and their scents permeate the air.
After he catches his breath, he flops back onto the bed next to him.
"Does this mean I can take you out on a date?"
Katsuki snorts and huffs out a slightly hysterical laugh. "Sure, after you get me a proper courting gift."
"Deal!" He scrunches his nose at his mess. "I'm gonna go clean up. Stay the night?" He gives his best puppy dog eyes.
"Fine. Only because I'm tired as shit now."