Posted originally on the Archive_of_Our_Own at https://archiveofourown.org/ works/11962890. Rating: Explicit Archive Warning: Underage Category: M/M Fandom: 僕のヒーローアカデミア_|_Boku_no_Hero_Academia_|_My_Hero_Academia Relationship: Bakugou_Katsuki/Kirishima_Eijirou Character: Bakugou_Katsuki, Kirishima_Eijirou, Todoroki_Shouto, Midoriya_Izuku, Jirou_Kyouka, Ashido_Mina, Kaminari_Denki, Sero_Hanta, Asui_Tsuyu, Aizawa Shouta_|_Eraserhead, Yagi_Toshinori_|_All_Might Additional Tags: Quirk_Swap, Anal_Fingering, Anal_Sex, Vibrators, Anal_Plug, Anal_Gaping, Anal_Play, Self-Lubrication, egg_laying_kink, Ahegao, Plot_What_Plot/Porn Without_Plot Stats: Published: 2017-09-02 Words: 4380 ****** But I can't kill with this... ****** by iroiroriro Summary A villain's quirk caused several of their classmates' personalities and quirks to switch up... And somehow, All Might thought of the great idea to try to have them switch their hero costumes too. And so, Kirishima has a bad time taking his eyes off Bakugou. ----- Based on the quirk switch artwork that Horikoshi drew where Bakugou switches quirks with Momo !! Notes See the end of the work for notes "But I can't kill with this..." Bakugou stared at the matryoshkas he made, a soft expression on his face. The items resemble him wearing his own original hero costume. Kirishima thinks it looks cute but saying that would probably make him angry... Or not? He can't actually predict his classmates at the moment, not with them being all jumbled up like this.   "I am the darkness, I am the night!" Todoroki shouts, covering half of his face with the black cape that was originally the design to Tokoyami's costume, Dark Shadow encircling him with an evil laugh. Kirishima sweats, he's probably gonna regret that later. The real Tokoyami sits quietly at the side, seemingly not caring about anything. "That's manly, Todoroki!!" Midoriya fist pumps, he's currently wearing Kirishima's costume, cheering for the 'Dark Knight'. His expression looks determined and his eyes are sparkling. "Woooooohooooooo!" A shout from Jirou makes him look up. She slides around the place with her acid, jumping everywhere and playing around. "Jirou, don't use too much all at once! You'll get dehydrated!" Ashido shouts after her, long earlobes with jacks at the end bouncing all over the place. "This is so cool!!!" Tsuyu gives off sparks on her hands, a big smile on her once blank face. At least she knows not to use too much at once. Kaminari stands beside her with his back bent and hands dangling down just like Tsuyu once did. "Gero," he comments, nodding. His face is blank save for the constant drooling he does every now and then which Sero wipes off with a towel immediately. He can't seem to get used to the shape of his mouth, his long tounge sometimes lolling out to dangle aimlessly. Unlike Tokoyami who retains his bird-like features, all the frog components of Tsuyu's quirk seem to have manifested on the once-electric boy. It would be hard to get used to, seeing that his hands and feet also seem to have changed their size to accomodate the quirk.  "You're mumbling again," Bakugou calmly comments, making Kirishima shut up immediately. "Oh, was I?! S-sorry, I didn't notice!!" He waves his arms around and apologizes. "It's not as long and detailed as Midoriya-chan's mumbling, though. And he only states the obvious too... Is it because Kirishima-chan's an idiot, gero?" Kaminari says honestly, earning a slap on his shoulder from Sero who bursted out laughing. "That hurts, Sero-chan," Kaminari slaps back, receiving a pained groan from the other, effectively stopping his laughing. "Hey, that's no fair!! Your hands are bigger so it hurts more!!" Sero complains, rubbing his back. "G-gero..." Kaminari deflates, tounge lolling out. He didn't mean to exert that much force but the quirk proves itself to be hard to control. Sero wipes his chin off the excess drool anyways. "Life's not fair!! Only painful and filled with distress and suffering!!" Todoroki announces, one leg propped up a table. "I don't really agree with that but you look manly and cool, Todoroki!!" Midoriya hardens his arms and punches them up. Whether it's on purpose or accidental is unknown. Tokoyami closes his eyes and facepalms, the only emotion he's shown so far. He doesn't remember being that dramatic... At least he seems to be getting along with Dark Shadow. "It's gonna be pretty hard to get used to that but ain't that great, Sero?" Mineta comments. Sero raises an eyebrow in question. "What is?" He asks. "You know, he's drooling a lot and his tounge is long and elastic if you know what I mean..." he finger guns. Sero turns beet red and he was about to scold Mineta for his dirty mind when an explosion sends him flying. "Stop being so fucking vulgar, you pissy ass fuckface!!" Momo shouts angrily. Kirishima cringes, hearing Momo shout and curse like that doesn't feel right. "But you're also being vulgar, Yaoyorozu-chan..." Kaminari hides behind Sero just in case. Momo's eye twitches, catching herself. "Crap, fucking sorry," Momo apologizes only to groan and slap a hand on her face. For some sort of reason, she can't stop cussing out. All Might enters the disheveled room and clears his throat. "Wow, you've only been here for a few minutes and it's already a mess!" Aizawa sighs beside him. Why did the big idiot think this is a good idea? "Anyways, how does your costumes fit? We had them custom made to fit your sizes so you'll be more comfortable!" He announces. To be fair, they all look good. Kaminari's a little uncomfortable with the spandex at first but it makes jumping and moving around with Tsuyu's quirk easier. Kirishima turns to look at Bakugou who pouts and pushes a matryoshka he made over, eyes downcast. There's an alarming amount of them now, he seems to really miss his quirk. Momo's costume hugs his body tight and doesn't cover enough. "Now that you've somehow gotten used to the quirk swaps, how about a little activity to have some fun?" All Might suggests. Aizawa grabs him by the collar and turns so that they're facing away the students. "What on earth are you doing??" He seethes. "It's not that harmful now, is it? It's going to wear off anyways so we might as well have some fun!" Aizawa groans and lets go of All Might. Why is he even here?   They went to the mock city in the training grounds to have them test out the quirks. All Might announces a treasure hunt of some sort and the more mobile students immediately head out. Sero wasn't affected by the quirk swap but the teachers allowed him to follow Kaminari lest he slips and hurts himself since he's not used to everything yet. Bakugou's fire seems to have lightened again as he tries to find the items with whatever he has. Kirishima follows around. "Why don't you go somewhere else? This is my area," he calmly says which seems to have irked himself due to the lack of usual bite. He growls forcefully and enters a building, kicking stuff and looking around. "It's okay, I'm not participating! I already told All Might that I'm not using Midoriya's quirk. It's too scary," he remembers how Midoriya uses his quirk during the first few months of knowing him. Nope, he doesn't want to break his bones for a treasure hunt, thank you very much. "Anyways, how's the creation quirk doing? You having fun with it?" Kirishima asks. Bakugou huffs. "Seems that ponytail is enjoying it more than I enjoy this."His point was further proven when they hear a loud explosion from far away. Man, she's having too much fun. "Hmmm, have you tried making stuff? Other than the matryoshkas?" Kirishima asks, eyes running down Bakugou's legs. He freezes when he catches himself staring at Bakugou's backside too long and immediately waves his arms around looking for an excuse. "N-not that I'm suggesting any particular thing!! I-i- it's just that you look pretty nice in that and I've been thinking if that thing is possible but-oh god wait why did I even think that? No no no no nevermind!!" His face burns red and when he looks up, Bakugou is inches away from his face. "T-t-t-too close!!! You're too close!!" He flails and before he knows it, his back is against the wall. "B-bakugou?" He croaks out, voice dry. Bakugou gives a small smirk and slowly runs a finger from his collar bone down to his navel. Kirishima's eyes follow the movement and he audibly gulps. "You like how I look?" He teases with a treacherous innocent face, pressing his body against Kirishima's and giving a soft moan upon contact. "B-b-b-bakugou????" Kirishima raises his hands, unsure what to do. Normally, he's the one who teases and makes Bakugou beet red but Midoriya's nervous nature pretty much stops him from doing what he wants to do. A thought suddenly goes in his head and he cringes. "Wait, is this Yaoyorozu's nature or...?" He trails off. Bakugou gives him a small flick on the side of his head. "This is all me. Just a lot more calmer now, I guess. Anyways, this is still me. My face would've already exploded from embarrasment," he pouts. That's cute. His pout slowly turns into a smirk and he slides his body against the other. Fuck, he really looks good in that. "So? You were saying something earlier, hm?" He guides the other's hands down to rest just under his ass. Kirishima gulps and cups it firmly, earning a chuckle that can be mistaken as a sigh. He traces the line where the cloth meets skin and suddenly grabs the material in a fist, pulling up. "Ah-fuck- What are you-" Bakugou groans and bites his lip, the material settles in between his buttocks and squeezes his crotch tight. Kirishima's right hand kneads his ass cheek in time with the pulling. His body rocks back and forth and he settles his hands on Kirishima's chest for stability. "F-fuck Ah... Woah..." Kirishima kisses his cheek, momentarily stealing his attention from the thing that's happening with his butt right now. "D-does it feel good?" He asks, red faced. The material tightens in between Bakugou's ass cheeks and rubs. He can feel his balls getting squeezed and his asshole throbbing, begging for attention. Kirishima squeezes his ass and moves a finger to dip in the entrance of his still clothed hole. A sultry moan escapes his lips. "F-fuck yeeeaaahh~ Mmmmhhh~" he moves his ass to feel more of the stimulation, unabashedly moaning. "Y-you think you can... Make a love egg in there?" Kirishima asks, sweating. "Wh-what...? Ah~" Bakugou arches his back, he can't understand what Kirishima is saying because whatever is happening down there feels too good.  "A-a love egg. Make one. I-i-i-in here," he stutters, finger circling Bakugou's puckered hole, stopping his movements so the other can understand what he's getting at. "...You want me to make a fucking vibrator in there???" He stares at the other incredulously. Kirishima gets redder and panics. "I-i-i-i-it's just a suggestion!! You don't have to-" He was cut off by a peck on his lips. Bakugou smirks and fishes Kirishima's phone out from one of the costume's pockets and opens it. "Sounds fun. Let me just search how it's made..." Kirishima gapes, he can't believe this is really happening. After a few moments, Bakugou gasps and almost drops Kirishima's phone. "W-woah, Bakugou! You okay??" he takes the phone from the trembling hand and puts it back his pocket. "F-fuuucckkk..." His attention goes back to Bakugou who's biting his lips too hard. "Hey, don't do that! You'll draw blood!" He realizes that the other's whole body is trembling and wraps his arms around him. "H-hey, what's wrong?" "I-It's too deep inside I... Ugh, fuuuuuck," he whines and leans his whole weight against Kirishima, ass sticking out. Kirishima's mouth falls open. He really did it. He really fucking did it and it's inside of him. Holy shit. He grabs on the other's garb again and pulls up hard, almost making him scream. "Kirishima, you fucker- not now I- FUCK!" Bakugou squirms, the tightness at the front of his costume making his dick throb. Kirishima pulls Bakugou's chin up for an open mouthed kiss and strokes his crotch, swallowing all the high- pitched moans into the kiss. Kirishima slides down the wall and pulls Bakugou with him, making him break the kiss and shake his head. "N-no, no- I don't wanna sit- I- fuck," Bakugou pants in a mess, knees trembling and ass sticking up in the air. Kirishima kisses his cheek and hums, stroking the other's now fully hard dick. Kirishima gulps. "Y-you think you can put another one in there?" He whispers, squeezing the leaking head through the tight costume. Bakugou whimpers, hips stuttering. He moves a hand to move the offending clothing, releasing his dick from its confines with a moan. He nods and braces himself against Kirishima. His grip on the other tightens and he squirms, face down and ass up. Drool starts to run down his chin and he feels a big lump just beside his cheek. "W-wait, B-Bakugou?!" Kirishima stutters out as Bakugou zips down his costume and pulls out his dick from the bright red boxers. "Y-you don't have to...Mh," Kirishima lets out a broken hum, thrusting his hips up when Bakugou squeezed his already leaking cock, licking from the base to the tip. Bakugou gazes at him. The tip of Kirishima's dick enters his plump mouth and he moans around it, sucking languidly. In a sudden flash, Bakugou is slammed against the wall, legs raised and trembling in Kirishima's hold. "B-babe, I-I can't..." he slowly thrusts his hips, huge cock sliding against Bakugou's, making him mewl in pleasure. He circles his fingers around the puckered asshole and enters with his middle and ring finger. Bakugou squeals and slides down the wall with a shudder. Kirishima stares as his classmate cries out in pleasure under him, thrusting his fingers in and out with so much force Bakugou has to grab onto the wall as his body bounces back and forth. "I didn't know you'll make them this big..." He can feel the strong vibrations with his fingers. Must be half the size of a baseball. Kirishima leans down to kiss Bakugou in the lips. "C-can I enter you, babe?" he asks. Bakugou shudders when Kirishima pulls out his fingers to align his cock in his entrance. Bakugou wiggles around for a comfortable position before he nods, gasping when he feels the head stretch him wide. "F-fuck- I sometimes forget how fucking big you are-" he groans as he's stretched even more. Kirishima curses when he finally reaches the love eggs, the strong vibrations making him come undone even faster. He tries pushing more, moaning loudly as he tries to stretch the insides of his classmate's ass even further. He feels a sudden wet feeling in Bakugou's ass as he moans out loud and grabs Kirishima's arms for support. "Bakugou, what's that?" Kirishima asks, testing the feeling and slowly sliding in and out. The other whimpers and shudders, holding onto his legs to stretch them further. "I-ah, tried to-mh, make some lube," he pants, eyes rolling back when Kirishima hits a delicious spot in him. "Fuuuck yeeeaaaah that feels so goooood, aahhhhh~" he moans out, letting Kirishima hold onto his legs, his own arms falling on either side of his head. Kirishima almost pulls out all the way and Bakugou raises his head in question only for the other to slam back into him. Kirishima has to slap a hand over Bakugou's mouth to muffle his scream, back arching and eyes open wide. He gets past the vibrators and he feels them going wild around his dick, throwing his head back with a loud moan. "Bakugou, oh-fuck- B-bakugou it's s-so fucking tight ah!" Kirishima moans and starts pistoning in and out of him mercilessly, panting like a dog as he drags the vibrators with him, torturing Bakugou's insides with tremendous pleasure. Bakugou is reduced to a moaning and whining mess, grabbing the other and leaving angry red marks on his sides. Kirishima lets go of one of Bakugou's legs and lifts the other higher, changing his position and making him face to the side. Bakugou claws the concrete, drool pooling on the floor. He turns his head and looks at Kirishima just in time to see him raising a hand. Kirishima's palm slams down his ass, making him scream. Bakugou chants Kirishima's name like a mantra, his tears streaming down his face as he gets overloaded with overwhelming pleasure, the continuous spanking adding to the pressure inside of him. He feels something hot pooling in his gut and gives out a last shout before all he sees is white. Bakugou clenches his ass and cums, bringing Kirishima with him as the sudden tight feeling pushes him over the edge, spilling his load inside of Bakugou. The pair lay panting for a while, Kirishima giving a few gentle thrusts to ride out their orgasm before slowly pulling out. He places his fingers around the other's hole when he exits, stopping the now unmoving vibrators from sliding out with him. Bakugou weakly goes on all fours, ass raised. "K-kirishima..." "Think you can make a few more?" The redhead asks, gently sliding two fingers in the abused hole presented to him. Bakugou whines and shakes the fingers off. Kirishima places a kiss on Bakugou's now reddening asscheek. "Okay," Kirishima smiles, pulling Bakugou's torso up and guiding his head to meet him in a deep kiss. Bakugou moans as Kirishima dominates his mouth, not having enough energy to fight back. "B-but is it okay if I... See you push them out?" He consciously asks once they part, a trail of saliva connecting their mouths. Bakugou's eyes widen at the question. He bites his lip and chuckles in understanding, shaking his head. Who would've known Kirishima's this much of a kinky little shit? He's not one to judge though, he's not any better. Bakugou goes on his knees and braces his arms on the floor, hips up and spreading his legs wide. "Three more and that's it, alright?" He says softly, voice strained from all the moaning and shouting he did earlier. Kirishima beams, nodding vigorously. He gasps and almost falls when he makes the third one, legs shaking. He made it so that the vibrations were weak but his insides are too oversensitive from the fucking they did earlier. He creates the fourth one and he gasps as it slides just above his prostate, moaning and writhing in pleasure as the four eggs bump into each other inside of him, his ass up in the air. He peeks just behind his trembling legs to see Kirishima staring at him with fire in his eyes. He holds Bakugou's ass up and licks the twitching hole. "K- kirishima... J-just one more..." he pants. Kirishima smiles at him and kisses his ass, entering the hole with his tongue. "Mmmhhh, Kirishima fuuuccckkk," Bakugou moans out, drooling. Kirishima strokes Bakugou's now hard member and licks the insides of his walls as far as he can go. The blonde haired boy clutches his abdomen and makes the last one, suppressing a loud moan when he feels all the five eggs take up space, the first one poking out a little from his hole. Kirishima gasps and bites his lip, slowly pushing the poking egg in. Bakugou shudders, legs parting wide, a very sultry moan leaving his lips. "K- kirishimaaa, t-too deep," he groans. Kirishima chuckles and slowly moves his fingers in and out, making Bakugou moan in pleasure. Wait, no... He's not moving? Bakugou realizes that he's unconsciously thrusting into Kirishima's fingers. A smile tugs Kirishima's lips as he leans down over Bakugou and licks his ear. "Does it feel good, Bakugou?" Bakugou mewls in response, hips wriggling. "Last one for me?" Kirishima asks and Bakugou groans. "I-ah, I said just t-three, r- right? AH!" He throws his head back as he feels Kirishima push the eggs deeper into him. They vibrate against each other and he feels every movement with every push. "M-mhh, f-fine... J-just last one..." Bakugou gives in and he feels Kirishima's fingers leave him. He takes a deep breath and feels the very last one take up space inside of him. His eyes shot up as he feels the eggs vibrating wildly against his flesh, fighting for space with nowhere to go. He shouts, tongue lolling out and eyes rolling up as he feels himself thrusting his ass up to nothing. "K-KIRISHIMA!!" He mewls. Kirishima's hand presses Bakugou's back so it arches, his other hand blocking Bakugou's entrance so the eggs won't go out. Bakugou writhes under Kirishima, trembling with over stimulation. His moans get louder and louder as he feels the heat pool in his stomach again. He moves his torso around to grab Kirishima's arm, wailing in pleasure. Kirishima cups Bakugou's cheek and strokes it gently, the once explosive boy holding on to his arm for dear life. Kirishima holds the other's hand and sits back to watch as he removes his hand to free the vibrators inside of Bakugou. Bakugou screams as he feels the first egg stretch out his hole and slide out of his ass in less than a second of Kirishima removing his hand, small splats of the lube trailing after it. He cries out, eyes rolling back and ass clenching when he cums once again, preventing the second egg from leaving almost halfway through. Kirishima groans at the sight of Bakugou's stretched out hole clenching and unclenching around the egg, cum dripping down from his ass down to his thighs. Kirishima shushes Bakugou's cries with a kiss, wiping his tears and moving the sticking hair out of his face. "You're so good Bakugou, so good for me... Come on, you can do it," he says softly. Bakugou holds on to him and he closes his eyes as he pushes the egg out of him. The moment it falls out, Bakugou's body collapses into a panting and whining heap, legs splayed open and hips still trembling from the weakening vibrations of the four eggs left. "B-bakugou..." Kirishima moans out and covers his mouth, staring at the mess. Bakugou's asshole gapes, giving him a view of the last few eggs resting inside of him. A good amount of lube drips out of his ass, mixed with Kirishima's cum. "Just a little more, babe. Come on..." He lifts Bakugou's exhausted body up, resting the other's back against his chest and lifting his legs up to rest on his spread ones, splaying him out for all to see. He spreads Bakugou's ass cheek and pushes down his tummy, making the other shudder and hold back a mewl as he feels the eggs slowly sliding out one by one. Bakugou pants, resting his head against Kirishima's shoulder, the exhaustion taking in. Kirishima nuzzles and kisses his neck, whispering praises over and over as he feels himself blacking out.           Morning the next day, the students got their respective quirks back and everyone rejoices in the common room, save for Todoroki who feels too embarrassed to even face Tokoyami. Tsuyu asks where Kaminari is and Sero says that he has a sore throat and is resting in his room, earning finger guns from Mineta. "It's not like that, you little-" Sero chases him around, earning laughs from their other classmates. "How about you, Bakugou? You passed out from exhaustion yesterday, didn't you? You should eat a lot today, since the quirk burns out fats," Momo states, earning a huff from a red-faced Bakugou, "I don't need it," he seethes and everybody sighs in relief. If he has the energy to get pissed so early in the morning, then he must be fine. Kirishima enters the common room, snacks in hand for Bakugou. "Hey, Bakugou! I've got you some snacks! Let's eat 'em together!" he beams. "Hey, you said it was for Bakugou! Why are you eating them too?!" Mina complains. Kirishima pouts and was about to reply when he receives a kick to his leg. "Let's just eat it in my room," he says, walking away. "Got it!!" Kirishima follows. "Glad he's okay now, though," Sero smiles. They all got really worried when they heard from Aizawa that Bakugou and Kirishima was sent back first due to the former passing out. "I don't think so, actually. He's walking around hunched over..." Momo worries and everybody says that he'll be back to normal after eating.       Bakugou collapses on Kirishima's bed and whines the moment they enter the room. "Thank fucking god we're back... Mhh," he wriggles on the bed erotically, brows pointed up in pleasure. "B-bakugou..?" Kirishima blushes. What's going on with him? Bakugou smirks. "You know, yesterday felt sooooo good," he moans out, lifting his shirt up and running his fingers on his skin. Kirishima gulps, watching as his classmate reveals more and more. His eyes widen upon seeing pink pasties covering his nipples. "What?" Kirishima looks at him in question. Bakugou lifts an eyebrow, motioning him closer with a finger. Kirishima sighs fondly and runs a hand on the other's exposed body, palms his chest... and stops. His eyes widen in realization as he squeezes the other's pecs. Bakugou gasps, back arching with the sensation. He has pellet sized vibrators under the pasties, directly on his nipples, giving off a soft hum of pleasure. Kirishima gives Bakugou a deep kiss, receiving a mewl which he gladly ate up as their tongues tangle together in moans and gasps. "I-ahhh- wait, I have a surprise for you..." Bakugou breathes out, pushing Kirishima away. "What is it, babe?" he asks, absently pressing down Bakugou's abdomen. The ashen blonde moans out and shudders with the sensation. Kirishima grits his teeth and pulls off Bakugou's shirt and pants, throwing them in an unknown part of his room, and freezes. He wears an underwear with the same material and design as the bottom of his costume yesterday. "Where did you get all these?" He asks, running his hand on the red underwear. "I made them last minute before the quirk disappeared," Bakugou replies, guiding Kirishima's hand to the small of his back. Kirishima gulps and pulls the back of the garment, watching as Bakugou writhes, hands grabbing the sheets and back arching up. "F-fuck, Kirishima, ah~" Bakugou moans, feeling Kirishima's hand play with the vibrator on his nipple, the other pulling the underwear with varying strength, and Kirishima's mouth biting and sucking on his neck. His hips move up and down with Kirishima's pulling, making Bakugou feel as if they're getting on even if they're not doing it yet. "Ahn~ t-that feels good but ah, t-that's not the surprise. Mnh!!" He bites back a moan when Kirishima uses his knee to put pressure on his crotch.  "What do you mean?" Kirishima lifts his head to look at his already panting boyfriend. "D-down there..." Bakugou points. Kirishima's eyes widen and immediately raises Bakugou's legs, folding him in half. He gulps before moving the cloth to the side, revealing a butt plug. He looks back at Bakugou and sees him lick his lips. "There's more inside."     End Notes I am a sinful human. Please drop_by_the_archive_and_comment to let the author know if you enjoyed their work!