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“What the fuck is this?”
“Your costume, for the party!” Kaminari exclaims, tossing shit on Katsuki’s bed with a triumphant flourish. “Ei’s eighteenth birthday is today and we’re mixing the celebration with Halloween, remember? Everyone is dressing up, but I figured you wouldn’t get a costume on your own, so I got you one. Todoroki let me use his dad’s credit card for it. It’s a big bad Wolf costume! Look,” he says, lifting items as he speaks, “ears, red jacket, tail.”
Katsuki narrows his eyes at the tail. “Are you fucking kidding me? That’s clearly a fucking buttplug.”
“What? No, I would never,” Kaminari says innocently.
“Yes, you fucking would, you shit.”
“Okay, maybe I did.”
“And what the fuck am I supposed to do with it?”
“I dunno,” Kaminari says, raising his hands defensively, “either wear it or don’t. I wasn’t really expecting you to. At this point I’m kinda just glad you aren’t exploding me.”
“Yet.”
“Huh?”
Katsuki bares his teeth in a grin. “I’m not exploding you yet.”
“Aaaaand that’s my cue to go,” Kaminari says, exiting the room hastily.
The door shuts behind him with a solid click. Katsuki stares at the plug. At first, he’d thought Ejirou had put Kaminari up to this. But he and Ei are keeping their hookups on the down-low, so this is just a typical Kaminari prank that happened to hit closer to Katsuki's interests than intended.
The thing is, though, he and Eijirou have been talking about having a threesome for a while now, and Kaminari has definitely come up as someone they’re both attracted to. It would make the perfect birthday gift. Katsuki’s eyes fall to the drawer he keeps his lube in. Since Kaminari knows the tail is a plug…
He grabs his lube, then his phone, texting Eijirou with his newly-formed plan.
_____
When he arrives at the party that night, he’s wearing the whole costume, the plug firmly situated in his ass.
It doesn’t take him long to find Kaminari, in an obnoxiously yellow and barely-there pikachu costume. “Oh, cool, you actually wore it.” Kaminari grins and gives the tail a tug, eliciting a grunt from Katsuki.
He glares at the hyperactive asshole. “Why the fuck would you do that?”
Kaminari’s jaw drops. “Dude, don’t tell me it’s actually in.”
“Of course it fucking is.”
“I thought you just shoved it down your waistband or something!”
“What kind of a fucking pussy do you think I am?”
“I don’t—I—”
“Hey Katsuki, Denki, what’s up?” Ejirou asks, cutting Kaminari off. “Nice costume. I wasn’t expecting you to wear one!” He gives the tail a tug of his own, making Katsuki grunt and clench his fists.
“Stop, It’s a plug,” Kaminari hisses.
Katsuki gives Kaminari a withering look. “Don’t just go around telling people whatever the fuck you please, shit-for-brains.”
Kaminari looks genuinely guilty, but before he can say anything, Eijirou speaks up, feigning surprise. “Really? Lemme see.”
Katsuki rolls his eyes, but allows Ejirou to shove his hand down his pants, fingers prodding the rim of his asshole, pushing the plug more firmly in. Ejirou draws his hand back out and casually licks his fingers, grinning. “Aw, you used the strawberry lube I got you!”
Kaminari, predictably, seems to be some combination of confused and horny at that. “Um,” he says, visibly sweating and red-faced, “well, I’m glad you like the costume. I’m... going to go get a drink.”
The last of his words come out in a rush, and he scuttles off before either of them can stop him. Katsuki frowns exasperatedly.
“I think we came on a bit too strong,” Ejirou theorizes. “I’m going to mingle. You fine with that thing in?”
“Fucking duh,” Katsuki says, pushing Ejirou away. “Go do your shit.”
Ejirou smiles, walking backwards. “Text if you need me.”
_____
That’s how Katsuki finds himself in the bathroom twenty minutes later, reapplying lube. He’s grateful he brought a little bottle just in case, but incensed this seduction is taking so long.
Deku is washing his hands when he leaves the stall, and apparently decides now is a great time to start up a casual conversation. “Hey, Kacchan! Wow, you're actually wearing a costume.”
Katsuki washes his hands as quickly as possible, drying as he walks to the door. His only response is a grunt of acknowledgement, but Deku doesn’t seem to mind, following him out into the hall regardless.
“Why is this tail shoved down your pants instead of tied to the waistband?” Deku asks, giving the tail a tug.
Katsuki jolts, stopping in his tracks and making a surprised and likely horny noise. Really? What about the tail makes it so fucking tuggable to idiots?
Deku has always been too perceptive and knowledgeable for his own good. His eyebrows raise, his face flushes, and he takes a step back from Katsuki, raising his hands innocently. “Sorry, I didn’t realize it was a—” his face turns a deeper shade of red “—is it a—? Uh, well.” He closes his mouth, his face practically glowing at this point. A moment of silence settles between them before Deku speaks again, hushed. “Why are you wearing that here?”
Katsuki’s a bit red himself, now. “None of your business.”
Deku looks about nervously. “So are you and Kirishima—?”
Katsuki growls in frustration, ushering Deku into a nearby supply closet. He closes the door behind them, then flicks the light on, glaring at Deku. “I am in the middle of trying to get laid. So you—” He pokes his chest in emphasis “—need to shut the fuck up and stay out of my business right now.”
“Oh, so you and Kirishima aren’t already—?”
“I’m getting him a threesome with dunce-face for his birthday, okay?”
“I thought you already got him a present, though?”
Before Katsuki can answer, the door to the closet opens, revealing a surprised looking Kaminari on the other side. “Sorry, I thought someone left the light on. I didn’t mean to… interrupt.”
Deku glances at the very minimal space between them and seems to sense the train of thought Kaminari has begun to go down. In an astounding moment of poor impulse control, he grabs Katsuki, pulling him further into the closet to make room. “No, no, come in. You’re not interrupting anything!”
This momentarily presses Katsuki up against Deku. Which means he can clearly feel the partial erection he’s sporting.
Well, the good news is Deku is another of the people both he and Ei had greenlighted. He could serve as a backup if Kaminari decides to run for the hills, which would be the smart choice in this scenario.
Yet, instead of running, Kaminari steps into the closet, squishing the three of them together. Deku’s erection touches Katsuki’s thigh again, and he breathes hard through his nose.
“So why are we in the closet?”
Katsuki ignores the question to text Eijirou.
“Just… hanging out,” Deku replies, after it becomes clear Katsuki won’t answer.
Eijirou replies seconds later, and Katsuki slides his phone into his pocket.
“Alright idiots, you both know I’ve had this plug in all party. The lube has already dried out once, so I don’t want to stick around much longer. You two, me, Ejirou. Foursome in my dorm room. Yes or no?”
Both of them gape at him uselessly.
Before either can answer, the door opens and Eijirou pops his head in, grinning. “Hey guys!”
_____
Fifteen minutes later, Katsuki closes and locks his dorm door with all four of them inside.
Kaminari is far more relaxed now that he knows what's happening, already stripping the crop top from his costume off. He flops down on Katsuki’s bed. “So, what does the birthday boy want?” He wiggles his eyebrows. “I’m game for whatever.”
Kirishima grins, sitting down in Katsuki’s desk chair. “I wanna watch.”
Katsuki strips his shirt off, then eases out of his jeans. “Well, I’m getting spitroasted for my troubles,” he kicks the jeans aside, “so do you want to fuck my ass or mouth?”
“Mouth!” Kaminari exclaims, patting his lap, “come on up.”
Katsuki turns to look at Deku, who’s standing by the desk next to Ejirou, silently watching with rapt attention. “Then you’ve got ass.” He moves closer to the bed, bringing his hand up to unclip the ears, but Ejirou interrupts him. “Leave them on, they’re cute.”
Katsuki narrows his eyes, but relents. “Fine.”
He joins Kaminari on the bed, hand going to the waistband of his ridiculous shorts to pull them down.
Kaminari stops him with a hand on his wrist before he can. “Don’t you want to give Ei a show? Try taking them off with your teeth.”
Katsuki glares at that, but Eijirou reacts with audible happiness, so he swallows his pride and bends until his face is level with Kaminari’s waist. He’s feeling a bit unbalanced by all the orders, so he puts a hand on either of Kaminari’s thighs, then licks his erection where it’s visible through the fabric of his shorts.
Kaminari’s cock twitches, and he makes a soft little noise, clearly surprised. Katsuki takes the opportunity to bite down on one of his thighs, making Kaminari yelp.
Satisfied, Katsuki moves back up to the waistband of Kaminari’s shorts, gathering the fabric between his teeth. Kaminari isn’t wearing any underwear underneath, and Katsuki is able to easily maneuver the fabric over Kaminari’s cock and down his thighs. Kaminari lifts his hips from the bed helpfully, expediting the process into something slow, but smooth.
Katsuki is just pulling the shorts off Kaminari’s ankles when the bed dips behind him. One hand comes up to tug Kaminari’s shorts out of his mouth, the other brushes scarred fingers over Katsuki’s nipple. “Do you care about your boxers?” Izuku asks.
Katsuki’s brow furrows. “They’re fucking boxers, of course not.”
“Good.” He can feel electricity begin to crackle across the body behind him. From his periphery, flashes of green spark as Izuku uses his quirk to rip Katsuki’s underwear off and throw it and Kaminari’s shorts aside.
Katsuki gapes after the discarded items, unsure of how to react. Heat pools low in his belly, his dick at least certain of how it feels on the matter.
“That was hot,” Ejirou says. When Katsuki turns to look at him, he’s palming himself, visibly hard through his clothes.
Izuku’s hand comes between Katsuki’s shoulders, slowly pushing him down to meet Kaminari, who’s sitting against the headboard. “Focus.”
Katsuki wants to be indignant at that. He even furrows his brow in preparation. Then Kaminari’s dick is right in his face, and Deku’s hand is spreading his asscheeks open, one thumb pushing under the flare of the plug to tease at his rim, and Katsuki finds that he doesn’t really care all that much.
He grabs the base of Kaminari’s cock and licks up his frenulum, starting off teasing and light. Kaminari moans and squirms at the touch, but before Katsuki can even be a bit triumphant at that, Deku is slowly tugging the plug out, and a breathy noise of surprise and pleasure cuts off anything else that might have come from his mouth.
The plug hadn’t even been big enough to reach his prostate, but he still feels empty at its loss, grateful when Deku replaces it with two slick fingers. “Wow,” Izuku breathes, “you feel ready already.”
He wiggles a third finger in, then pushes them all deeper, mercilessly efficient as he searches for—and quickly finds—Katsuki’s prostate. “Fuck,” Katsuki moans. “Yeah, I’m fucking ready. Quit screwing around and fuck me.” He had that plug in for an hour, he’s more than ready.
“If you say so,” Deku responds, seeming amused.
Katsuki returns his attention to Kaminari, resolving to cover his own embarrassing reactions by making Kaminari react louder. He breathes deeply through his nose, guiding Kaminari into his mouth and sliding slowly down.
Then, he relaxes his throat, taking him further.
“Oh my god,” Kaminari moans, “holy shit.”
Katsuki’s lip twitches in victory around Kaminari’s cock, smug as he buries his nose in Kaminari’s short pubic hair and swallows around his dick.
“Fuck,” Kaminari swears, half a sob.
Katsuki feels warmth against his entrance, the head of a condom covered cock pressing against it. “You ready?” Deku asks.
Katsuki doesn’t bother replying, just focuses on sucking as he lifts off Kaminari’s cock, bringing a hand behind him to grab Izuku’s ass and push him forward.
The slick head of his cock pushes into Katsuki’s ass, and he moans around Kaminari. Shit, he never got to see the nerd’s dick, he didn’t realize how fucking thick he was.
He hears chuckling to his left, and lifts a hand to flip Ejirou off. The bastard clearly saw exactly how big Izuku was and chose not to warn him.
There’s a sharp noise, and his asscheek stings. He jolts in surprise, making a muffled, high pitched noise he never would have expected to come from himself. “It’s Kirishima’s birthday,” Izuku reprimands, even as he slides further into Katsuki’s ass. “Be nice.”
Izuku spanked him. He fucking spanked him. In any other situation, Katsuki would be livid, but milliseconds later, Izuku’s cock presses far enough inside him to reach his prostate, lighting his stomach up with fluttering electricity, and he suddenly couldn’t give less of a fuck. He squeezes his eyes shut, distracting himself from the embarrassing urge to drop his hips and desperately grind against the nearest pillow by taking a deep breath and sinking all the way down on Kaminari’s dick again.
Katsuki ignores the slow pace Izuku is setting, raking his nails down Kaminari’s thigh and starting off at a mid-level pace, bobbing up and down. Kaminari moans and swears, fisting a hand in Katsuki’s hair. One of the wolf ears falls off, but Katsuki ignores it.
Izuku starts fucking Katsuki harder, angling his thrusts down so they scrape against Katsuki’s prostate more intensely each time. Suddenly, Katsuki is unnervingly aware of the way air brushes against his cock and nipples. He doesn’t touch either, unwilling to come as embarrassingly soon as that would make him. Instead, he pulls off Kaminari, jacking him off as he sucks two fingers into his mouth, getting them wet.
His mouth is back on Kaminari a moment later, sucking him harder and faster, but more shallowly now. He brings his slick finger to circle Kaminari’s asshole. “Yes,” Kaminari hisses, gripping his hair tighter.
Katsuki takes that as an invitation to slide the finger in, pressing forward until he feels Kaminari’s prostate. He presses into it, and Kaminari whines. “Fuck. Second finger, I’m close.”
Katsuki complies, shoving his other slick finger in along with the first and rhythmically rubbing them against Kaminari’s prostate as he sucks his dick. Every now and again, Izuku presses just right into Katsuki, and he can’t help but moan around the cock in his mouth, but he does his best to ignore it and press on until Kaminari is choking on a warning.
Katsuki pulls off just in time for Kaminari to come all over his face. He screws his eyes shut, accepting his fate and working Kaminari through his orgasm with a hand on his cock and two fingers up his ass, earning himself two more spurts of come. Kaminari exhales a shaky moan, clearly done, and Katsuki retracts his hands.
As soon as he does, Deku slips out of him. “Hey—” Katsuki begins, but cuts off as he’s flipped onto his back, then turned across the bed so his head hangs off the side and his ass is in Deku’s lap. He blinks owlishly up, and Ejirou smiles back down at him, cock in hand. “My turn.”
Obediently, Katsuki opens his mouth, letting Ejirou press in, starting a quick, shallow pace. Izuku adjusts himself and slides back in, and Katsuki fists his hands in the sheets, feeling a bit used and embarrassingly turned on by it.
Deku’s hands squeeze almost painfully tight against his thighs as he starts a grinding, languid pace that sets Katsuki’s nerves alight. He’s close to the edge, frustratingly so, unable to tip over, and is about to touch himself when suddenly he feels warm pressure against his dick, too wet to be a hand.
Fuck, Kaminari must be giving him a blowjob.
His hips can’t decide whether to grind back into Izuku’s dick or up into Kaminari’s mouth, but when Kaminari's lips close around Katsuki’s cock and he sucks, it isn’t a problem anymore, he’s too busy arching his back and coming hard in Kaminari’s mouth, seeing stars as Kaminari swallows it all, and Deku grinds against his prostate, and Ejirou fucks his mouth, overwhelmed with all the different stimulus competing for attention.
Kaminari pulls off just as all the sensation starts to get painfully overwhelming, and seconds later Ejirou’s pulling out of his mouth as well. Katsuki feels the familiar sensation of come splashing between his tits as he blinks up at Ejirou.
As soon as Ejirou finishes, Deku pulls out, tugs Katsuki’s legs until his head is resting on the bed, and strips the condom off, crawling up to his torso to stroke himself until he’s coming all over Katsuki’s face in messy stripes.
When the last splash hits his face, silence settles in the room. Katsuki licks his lips and raises to his elbows, cautiously opening his eyes.
Kaminari’s stupid grin is the first thing he sees, hovering over him. “Y’know, I hear that stuff’s great for your skin.”
Katsuki sighs, flopping back, then bucks his hips sideways, ruthlessly tossing Deku off him to crash onto the bed by Kaminari with an “oof”.
“Go get me a fucking cloth.”
“I got it!” Kaminari says, far too energetic as he bounces away. Katsuki rolls his eyes, then tilts his head back to look at Ejirou, who’s practically melted into his desk chair.
Ejirou grins, and Katsuki can't help but smile back at him. “Happy birthday, Ei.”