Chapter Text
Izuku's brain was running a thousand miles an hour, as opposed to his normal 500. Katsuki's stare was empty and rage-less, which only incited Izuku's panic further. They'd been smacked by a villain during an encounter and were awaiting Recovery Girl's report.
The OfA user was frantically trying to figure out what was going on. When they were initially hit, Katsuki had the same thoughtless stare he held currently, while Izuku was bombarded with something he could only describe as super-powered thinking. Obviously, the quirk had seriously affected Katsuki since he was screaming just moments before going silent and...pretty much unresponsive besides being able to grunt and follow Izuku's movements. He was able to stand and pivot a bit, too.
Izuku had tried to bolster Katsuki to get them to a medic, but as soon as he touched the other hero, his own brainpower shut down, dropping him entirely. His thoughts were sludging through molasses and tar. He could recognize Katsuki's concern, confusion, and frustration. He could kind of mumble unintelligibly. It felt as though Denki had shocked him nearly to death.
Katsuki then tried to carry Izuku, reversing their situations once more, dropping Izuku to the floor. Izuku realized they couldn't touch one another unless they wanted to flip. He told Katsuki to stay right there, knowing full well he wasn't going to go far very quickly, and ran to get a couple shock blankets. He wrapped them around the blonde, being absolutely sure not to come into contact with him. And then, the greenette hoisted Katsuki into his arms and Float his way to UA.
By the time they landed, Katsuki had mustered a small scowl, Izuku assumed it was due to being carried like a princess. The other apologized with a chuckle as he plopped Katsuki onto one of the cots. The explosive one clearly struggled immensely to sit up in the cot, scowl deepening a little.
Izuku explained all he could to Recovery Girl before tapping Katsuki, giving him the chance to give his perspective to Recovery Girl. To no surprise, they'd had the same conclusion. The quirk only allowed one of them to fully function at a time. One having heightened thinking abilities, while the other was barely able to make sounds. Katsuki did add that, if he fought really hard against the quirk, he could regain some very basic movement and such. He barked at Izuku to use "his stupid genius quirk brain" to figure this out and tapped him to give him the brain power to do so.
Izuku tried to suppress the fluttering in his heart at Katsuki's gesture. He believed Izuku was their best chance to figure out what was going on and correct it. It filled him with confidence, pride, and an unreasonable amount of affection. He fully committed to thinking about the quirk, pacing and mumbling up a storm. The hero entirely missed Katsuki's mutely surprised expression.
"Nerd," Katsuki mumbled, slurred and hard to decipher. Izuku's head whipped over to see the smallest prideful smirk, the other clearly proud that he was able to say something through the quirk.
"You're able to talk! Good job, Kacchan! And so fast! You're amazing!" Izuku beamed. "Do you want me to switch with you so you can talk more?"
Faster than Izuku had ever seen, Katsuki's ears turned bright red, flush threatening to spread to his cheeks, and his smirk turned into a drop of worry. Izuku wondered if the quirk inhibited Katsuki's normal control over his facial expressions. He felt like he could read the blonde's expression better than he ever had before. "Let me know what you're concerned about Kacchan! Slowly, though, so I can keep up with you."
Izuku pat Katsuki's shoulder. Immediately, he was slammed with sludgy quietness. His body drooped and he felt heavy. Katsuki smacked his own face concerningly hard, weird. "Shitty nerd! I was trying to tell you not to fuckin switch!"
Izuku felt anxiety bubble from somewhere in the back of his mind. It...oddly didn't feel like his own. That must be the quirk. He didn't like making Katsuki mad.
"Sssssorrrryyy," he worked out slowly. Katsuki's scowl returned fully.
"How the fuck did you figure out how to talk so fast? Shit took me forever," the explosive hero said with a twinge of annoyance that was dampened by how red his face was. Pride poked it's head into Izuku's incredibly limited awareness, pulling the most minute quirk of his lips.
"One," Izuku pushed out. Katsuki's eyebrow raised before he looked entirely offended.
"Are you trying to say you're number one?!" Izuku huffed in attempt to laugh. Suddenly, he was looking at the floor. Why was he looking at the floor? Shoes are dirty.
"Good to know my gloves are good enough to let me smack you without switching again," Katsuki barked a laugh.
"You could have figured that out without violence, young man," Recovery Girl quipped as she entered the room.
"Oi, he was makin' fun of me!" Katsuki barked back. Izuku huffed again.
"I'm sure he was, given that he can't even stand up straight on his own. I have information on the quirk. Who wants to be the one to hear it?" she continued.
Katsuki groaned, "Should be the shitty quirk master." Fabric rustled before Izuku was flicked on the forehead, transferring the quirk once more.
He stood up straight and turned to look at Recovery Girl, "We figured out how to fight the quirk enough to say a word or change our expressions a little. So, yeah, I was totally making fun of him."
She rolled her eyes, "I can see why the teachers have a betting pool about you two."
"What?" Izuku asked.
"Nevermind that. The quirk is called--"
"Hah?" Katsuki responded, probably to the betting pool comment, but a few seconds later than he wanted. Izuku could pretty much feel the impatience growing within Katsuki. He couldn't help but send him a shit-eating grin, the one he often tried to explode off of his face. The blush returned to his ears, which made Izuku a little giddy.
"The quirk is called Brain Swap. When two people are hit, one takes on a significant amount of the other's thinking power, while the other person is left in a zombie-like state. You can change who has the brain power by touching. It should wear off in a few days. As you have already discovered, one can fight against the quirk and regain some functions. The more stubborn you are, the more likely you will gain more function back. It's no wonder you two problem children are already forming words," she tsked at them.
"A few days of this? That's not going to be easy to deal with," Izuku responded, glancing over to check on Katsuki. His hands were in loose fists and eyebrows scrunched together. He didn't like this either. "Is there any way to undo it? Can the villain reverse it?"
"He can, but he is uncooperative. I found the information I did because he was stupid enough to file his quirk details with the government," the old woman replied, leaning on her cane. "I already notified Eraserhead. He would like you both in class and figures you two can work together to learn something."
"Kacchan, I'm gonna swap with you so you can ask anything you want to," Izuku prefaced before poking Katsuki's hand, now that it was gloveless.
The taller one shook his head out, as though diminishing the last of the fog. Izuku stared at the way those soft spikes settled back into place, shiny in the awful hospital lighting. "So, what? Are we supposed to just babysit the braindead one and trust that the one with the fuckin braincell will trade it eventually? What a load of shit. How can there not be another way to get rid of this?"
Recovery girl raised an unimpressed eyebrow, "Bakugou, are you implying you don't trust your future hero partner to keep you safe and give you equal time to think?"
An icy feeling mixed with Izuku's own muted sadness. Katsuki doesn't fully trust him still. He frowned and slowly lowered his head until he was looking at his hands. He saw Katsuki turn to look at him.
A sigh came from the grumpy man, "I didn't mean it like that. I meant...there's just gotta be another way. I don't like having to decide who should think and when."
"Unfortunately, that's how it's gonna be. Why don't you guys head back to the dorms and clean up? I am sure if anyone can manage the effects of the quirks, it's the infamous Wonder Duo," Recovery girl commended, placing her hand on Izuku's shoulder in comfort before probably leaving the room. Izuku wasn't exactly sure, as he hadn't been able to look up still. The effort was exhausting and his head was heavy.
Izuku blinked slowly and was startled when he opened his eyes to see red ones staring at him sadly, tensing a full 10 seconds after opening his eyes. Katsuki had kneeled down to his level to make sure Izuku was looking at him. Affection fluttered somewhere in the depths of the fog. Kacchan was so thoughtful.
"Sorry, you know I suck at words. I trust you, okay? I wouldn't have asked to debut together after graduation if I didn't," the normally gruff voice was soft and soothing. Izuku felt his shoulders relax, sagging from their positions by his ear inch by inch. "Better. I think you'd get us to the dorms faster, but could I shower first? I don't want to be covered in nitroglycerin while I'm a fuckin zombie."
Katsuki pat Izuku's head, transferring the quirk once more. Izuku carefully help remove Katsuki's hand without touching him, smiling at the other. "Yeah, no one needs to be exploded by the world's slowest grenade," the smaller one laughed as Katsuki let out a delayed growl. "Let's get moving."
An awkward carrying situation and another poke later, Izuku was left braindead in his room while the other went to shower. Katsuki was done with his homework for the day already, so he'd come back and they'd trade again so Izuku could do his homework and leave Katsuki in his own room. Izuku tried to convince him that they should sleep over at one of their dorms, just to make it easier to trade. Katsuki was adamant that wasn't necessary, though. He said he'd ask Momo for a device they can keep on them. A simple touch recognition device that would alert the other to go check on the brain dead one. Some "Life Alert bullshit."
Izuku was willing to bet that Katsuki wanted to see how hard he could push the quirk and did not need an audience for that. He knew Izuku wouldn't agree unless there was a way to ensure he knew if Katsuki needed anything. It still made the OfA wielder uneasy and left him wondering how much Katsuki really did trust him.
He only managed to have a couple complete thoughts before Katsuki slunk back into Izuku's room, hair dripping onto a towel around his neck. He wore the black tank top and gray sweat pants that haunted Izuku's fantasies. He cursed the quirk as his face burned hotter than ever. He was so glad that his hero-ing underwear was designed to keep things smooth and protected while in uniform because that would also pose a problem.
"Whoa, don't tell me you got a shitty fever or something," Katsuki asked, moving to place his hand on the reddened forehead before remembering the quirk. Izuku just barely shook his head no. "Good, we don't need that shit right now. Let's get back to my room so we can trade. Wanna try walking there yourself since you're so fuckin stubborn?" Katsuki said with a false snarkiness. Izuku nodded his head once, pulling a tsk from the other.
"Of fucking course you can nod so easily already."
Izuku smirked the best he could, which was not great. He channeled the herculean mental effort he learned to weaponize with OfA and stood up. He slowly shuffled toward the door. His body was just as embedded in tar as his thoughts, every step radiating a burning sensation with the effort it took.
"The fuck, nerd? You look like you just got blasted through a few buildings instead of getting hit with a zombie quirk. How in the hell are you doing that?" Katsuki spoke in his usual loud tone, competition and irritation bleeding into his words.
"Prac....tice," Izuku forced out, nearly panting with all of the effort he was using. His hand slowly extended to lean against the wall. Katsuki noticed and placed the towel that was hanging around his neck to now cover his arm. He showed Izuku, who carefully moved his other arm to brace himself on Katsuki as well, burning red once more. Thankfully, Katsuki let it slide.
Katsuki made a sound of confusion before grunting as they began to walk once more, "Do you mean that all that bullshit with OfA is making this easier for you?"
"Ya."
"Stupid chosen one bullshit. It's only because I was already so fuckin strong. If I had OfA, I would have blasted every villain off the face of the fuckin earth," the taller one grumbled angrily, opening the door for Izuku and keeping pace.
"Kac--chan...best," the greenette managed as they walked down the hall at snail speed. He glanced to catch Kacchan's ears turning pink. Moving his eyes was pretty easy, now.
"Shut up, dork. You're the one who is destroying this quirk. You'll be normal before it wears off at this rate," Katsuki responded, pointedly not looking at the other. They were almost to the elevator, much to Izuku's relief. Walking felt like using 80% OfA. It hurt.
They eventually made it to Katsuki's room. The blonde flopped on his bed, making himself comfortable before extending his hand, "Just come trade me again before bed so I can brush my teeth and all that shit."
Izuku barely had to shift to tap the out-stretched hand. Suddenly the weight was lifted off of him and clearly fell on Katuski. He caught his breath for a moment, "Walking with the quirk is really hard. Thank you for helping me, Kacchan. That was really nice of you," Katsuki's face tried to contort in anger as his blush returned. Izuku really enjoyed seeing the stoic one fluster. "Anyway, I still think we should just have a sleepover. It makes no sense not to."
Katsuki twitched his hand and Izuku took that as an indicator to trade again. Tap.
"I won't be able to focus on shit with your sloth-ass around. I'll have to think about if you need to talk or not, which, you always fuckin talk," Katsuki responded before slapping Izuku's hand hard enough to sting. Their hands were just suspended in the air now as they were used as the equivalent of a talking stick.
"But going back and forth makes no sense either. How are we going to get ready in the morning? Make breakfast?" Izuku asked, passing the proverbial talking stick once more with a notably gentler touch.
"I'll make us breakfast, dumbass. We can take turns getting ready, just like we are tonight." Slap.
"Kacchan, I don't think we will have the energy to walk so much. I feel like I've been fighting for hours just from walking here." Tap.
"What, are you a weak little bitch?" Thwack.
"Alright, go ahead and walk to the bathroom, Kacchan," Izuku challenged, crossing his arms and delivering a hard stare. He backed to the desk to give Katsuki space.
The blonde grunted and worked to sit up. He fell back a few times, grinding his teeth almost audibly. He managed to stand up after a few more attempts. Izuku saw sweat drip from his forehead. He took two steps over to Izuku, panting by the time he was done. He bent over, which was more like letting himself fall forward, to headbutt the greenette and trade the quirk.
"Fuck you," he wheezed, hands going to his knees. "What the fuck are you made of?" He caught his breath for a minute before smacking Izuku.
"I told you, training with OfA helped a lot. It feels like how it used to in the vestige realm, and when I was just unlocking all of the quirks," the wielder explained, flicking the suffering one.
"Okay, fine. You can stay in here tonight. I ain't sleeping with All Might staring at me. Bring your mattress from your room," the blonde responded, settling in bed once more. He punched Izuku's arm when he was comfortable again.
"Thank you for finally being reasonable, Kacchan. I'll be back," the smaller one left to shower and get ready for the night. He felt weirdly guilty that he was progressing so much faster than Katsuki was. This competition didn't feel fair, for once. And it gnawed at Izuku.
His head was spinning as he showered and packed an overnight bag. Katsuki should probably be the one who is aware during Math and English, as those were his best subjects. And maybe Battle Strategies, too, since he got higher on the last test. Izuku would take Quirk Theory, Hero History, and Physics. Who should get it when they sleep? Katsuki is an early riser and offered to make breakfast, so he should probably take it.
He knew he was muttering as he lugged his mattress to Katsuki's bedroom, opening the door and flopping it down on the ground. Katsuki startled almost in time with what would be expected. He was standing at his desk, phone in hand. He'd look normal except for the sluggish turn he completed to face Izuku, red from exertion. He looked exhausted. The last time he looked so tired is when they had a few days off and decided to see who could fight the longest. They both lost when they had to be transported to Recovery Girl by Eijirou.
"Kacchan, I know you want to be able to break through the quirk as much as I can, but you're going to over-exhaust yourself," Izuku warned gently, walking over to tap Katsuki so he could get a chance to breathe.
The hulking form slunk over, taking deep breaths. "It's not just to catch up to you, you prideful little shit. I don't wanna be a fuckin potato for half of the next few days," he responded, agitation taking over the air in the room. "It...reminds me of the vestige realm, too. I don't exactly like that feeling. It's not as shitty when I fight back." Izuku felt a weight sink into his stomach. He forgot that Katsuki was briefly in the vestige realm with him just two years ago.
Katsuki stood up, rolling his shoulders back before returning the brain power to Izuku. "I'm sorry, Kacchan. I didn't realize it felt the same for you, or that you remembered what it felt like. That can't be pleasant to relive. Why don't you let me be a potato tonight and through breakfast? Get a good break from it. Then, we can trade off during classes. I think I have it all worked out." Izuku touched Katsuki to return the quirk.
"English, Math, and Battle for me and Quirk Theory, History, and Physics for you?" Katsuki questioned. Izuku nodded slowly. "Cool. Sit down on my bed and I'll fix yours. Then we can get some damn sleep. Did you brush your teeth and all that shit?"
Izuku gave Katsuki a small smile, though it felt so big in his heart. "Yesh!"
Katsuki cleared his throat before moving to set up the mattress that laid haphazard on the floor. The greenette leaned against Katsuki's bed as the other moved the mattress so it was neatly beside his own bed. He smoothed all the sheets down and laid the All Might blanket on top nice and neat. He huffed a laugh, "Can't believe you still sleep with your All Might set."
"Cozy," Izuku slurred out. He almost saw a small, affectionate smile tug at the other's lips as he folded the corner, just like he always did for himself. Izuku sluggishly enjoyed that there were aspects of Katsuki that remained the same after so many years and wars.
"Whatever. Need help getting into bed?" Katsuki stood up to address Izuku. Hesitation was baked into his features, but it was a really nice offer. Thoughtful. Just like making the bed, even though it was perfectly fine as a heap on the floor.
"H-help...down?" Izuku asked, hoping he was clear. Katsuki nodded.
"Help you down?"
Izuku hummed in affirmation. Katsuki grabbed some gloves off of his desk, just normal ones he kept around for cold days. He picked Izuku up by the waist and moved him over the bed so his feet were at the end of the mattress. The quirk made it so he turned red from roots to toes, despite Izuku fighting with all his might.
Katsuki braced his hands on Izuku's arms and together, with great and careful effort, they lowered Izuku into the bed. He couldn't help but be distracted by those insanely buff arms as they lowered him. The veins and muscles protruded as they slowed the descent in order to keep Izuku from busting his ass. God, he was down so bad and the quirk was not helping him. Katsuki untucked the blanket he had literally just set up so nicely, and threw it somehow perfectly on top of Izuku.
"No...tuck...in?" Izuku questioned, shit eating grin barely breaking through the stone face effect. Katsuki snorted.
"What are we, 5?" he laughed as he moved towards the bathroom.
"Miss...it." Izuku whispered, feeling a wave of panic. He didn't mean to say that. The quirk lowered inhibitions entirely, which was so problematic.
He was too busy panicking at the speed of sludge to see the blush Katsuki had been overwhelmed with, tucking himself into the bathroom until it went away.
It was about that moment when a thought bubble emerged from the goop of his brain. There was no need for Kacchan to have made the effort to help Izuku. They could have just traded the quirk over. Why would he go through so much effort?
By the time he'd finished thinking that question, the lights were turned off and Katsuki had muttered a good night. The greenette was asleep before he could even so much as grunt, wiped out from fighting the quirk.