Work Text:
The calibration of the sensors on Izuku’s boots was a delicate process. It required focus and a careful, steady hand. He'd been working on them for the better part of an afternoon, the sleeves of his coverall tied around his waist as he delicately maneuvered wires with a set of tweezers. Though his experience with his bracers had helped give him some idea of what he was doing, these required multiple, different units of measurement. It was why he’d put it off for so long, after all; he was much better at coming up with ideas than he was at executing them, generally speaking.
So, the door to the development studio slamming open as loudly and abruptly as it did was about as helpful in keeping a steady hand as one might expect.
“Oi, Dek—Izuku!”
Both of Izuku’s hands had twitched so violently that the boot twisted, causing a small, obnoxiously bright red flashing light to go off within the maze of wiring under his fingers. Izuku had jumped too, though the sight made him forget his fear as he groaned in disappointment and slumped over, his forehead hitting the tabletop.
“Nice job.” Katsuki jeered as he walked over to his workstation, dressed in his costume sans gauntlets, mask, and boots. The dark soot across his sleeves and upper half suggested he’d just been in an exercise.
Izuku picked up his head to glare through the yellow-tinted goggles over his eyes.
“Thanks, Kacchan. Now I have to start over. I was at that for over an hour!”
“Get better. Then maybe you won’t have a problem.”
Izuku’s expression flattened, and Katsuki rolled his eyes dramatically.
“Fine. Sorry, or whatever.”
He slammed his hand down onto the table as Izuku sat up and tilted his head. When Katsuki pulled away there were two black earbuds; at least, that was what they looked like they had been. They were smashed to hell. Izuku picked one up and watched it droop towards the table, the ear piece only held on by a few delicate wires. He looked past it at Katsuki like he was in pain.
“These were steel. How did you even manage this??”
“Don’t blame me.” He snapped, crossing his arms over his chest and turning his head away petulantly. “Blame that metal-head in B. It popped out of my ear and he stomped on it.”
Izuku slid his goggles onto his forehead, his green fringe pushed back with them, and sighed. He loved making support equipment, but his mentor, Yuuki, had been right once upon a time when she told him that heroes would always need a way to combat the sheer number of quirks out there in the world.
“And this one?” Izuku asked, setting down one to pick up the other. It had been pancaked, rather than separated, and Izuku almost dreaded the answer—because he had a sneaking suspicion he knew what it was.
“Kirishima.” Katsuki grumbled as Izuku dropped his hands to the table, exasperated. Bristling, Katsuki pointed accusingly in his face and exclaimed, “Hey, it’s not my fault you made them so shitty that they keep falling out!”
Scooting his boot sole off to the side, Izuku pulled a notebook out of a drawer at his right. He flipped a couple of pages until he found the sketch of the two earbuds in question and looked over them for a moment, reacquainting himself with the design. It had been a few weeks since he’d looked at them last. Setting the notebook down on the table, he leaned against it and scrutinized Katsuki’s costume.
As far as the design went, despite having a mother and father in the business, Kacchan’s costume was fairly low-key. Izuku already knew he’d come up with it himself for the design studio to replicate, from his clunky black boots to the grenade-like gauntlets on his arms.
Although it was good; and it was, Izuku thought, a very good costume, he would have loved to make suggestions to improve it. His gloves in particular were a point of interest for Izuku’s constantly ticking brain, which couldn’t help but try to come up with a way to better store his sweat closer to his palms, without constantly lugging around his gauntlets. They were cool and very on brand, but they tended to get taken out quickly in a fight. He needed something more reliable.
Not that Izuku was about to go around saying that. Kacchan had gotten better over the past year, but not good enough to accept that kind of help.
Reminded that he was supposed to be thinking about the ear pieces, not the rest of the costume, Izuku closed the notebook in front of him and considered their options.
“Well, the easiest fix would probably be a band—“
“What do I look like, Dunce Face? No way.” Katsuki interrupted, and Izuku had to resist rolling his eyes.
“Okay. Or I can do a piece that wraps around your ear. They might be a little uncomfortable if you wear them for long periods of time, but they’ll stay on better.”
“Rather have my ears hurt than my hearing go. Do it.”
Katsuki’s hearing had already started to go, and no thanks to his quirk. Even the smallest explosion was loud enough to cause harm over a long period of time, and they happened, more often than not, right by his head.
That was why Izuku had started working on the designs in the first place. The set of earplugs he’d made for Shouta, extra though they were, had given him the idea to work on something similar for Katsuki. Similar, but more specialized for his particular needs. He needed to be able to hear conversation and callouts, while also blocking out the harmful sound of his quirk constantly firing off.
To his credit, Izuku had done exactly that. Making the dampener activate only when the sound around Katsuki reached a certain decibel achieved exactly what Katsuki needed, keeping his eardrums safe and his hero work largely unaffected.
Mitsuki had all but suffocated him when he’d told her over dinner, relieved at knowing her little brat wasn’t going to lose his hearing at the tender age of 16.
And Katsuki, for his part, had taken the gesture in stride. There were no gratuitous thanks or gushing praise; not that Izuku had expected either of those things. Instead, he’d gone for smaller, but still glaringly obvious changes.
He started calling him Izuku, for one. Though he still didn’t have it exactly, prone to calling him Deku in frustration or mocking, he was trying. Even after Izuku assured him that he didn’t mind it so much anymore, he wouldn’t budge.
More interestingly, he had also taken to sitting down with Izuku and his friends at lunch every once in a while. The move confused not only Izuku, who was delighted, if slightly alarmed, but everyone else, too.
The first time he’d practically pushed Todoroki’s tray of soba out of the way to make room for his own food, Shinsou had looked between Izuku and the blonde like he was ready to throw hands. Upon realizing that every set of eyes at the table was trained on him, (along with the eyes of people not at that table; his usual squad of lunch-mates were gaping too, just from a distance) he’d scowled and snapped, “What? Take a fucking picture.”
He went back to his lunch, and everyone else made pointed eye contact. Uraraka, Iida, Todoroki, and Shinsou all turned to Izuku, who shrugged with bright eyes. Deciding it wasn’t worth a fight, they turned back to their lunch trays, too.
For Izuku, all that mattered was knowing the gesture was appreciated.
Even if it didn’t look like it at the moment.
“Fine.” Picking up the two pieces of what were essentially scrap, Izuku pushed the stool he’d been sitting on away and slipped them into one of the pockets of his green coverall. “I’ll go gather the supplies and get started.”
He paused, looking analytically over Katsuki’s costume again.
“Is there anything else I should add?”
Katsuki waved him off and turned to leave. “Not unless you’re putting comms or whatever in them, but good luck getting the okay for that.”
Izuku’s expression pinched. Yeah. Not happening. Mr. Maijima, the excavation hero Power Loader, already had to disassemble and reassemble his work to make sure he wasn’t up to anything fishy. No way was he going to be approved for comms when those components had been the first thing he’d snagged in his first year at UA.
“Right. I can give them to Shouta when I’m finished with them to give to you, if you want. Or I can bring them to the dorm?”
Already opening the door, Katsuki rolled his eyes. Not that Izuku could see it.
“Just bring them over, nerd. I think you can handle that.”
“I know I can handle it!” Izuku’s voice raised slightly to follow Katsuki as he left, and he stuck his tongue out at the door once he was out of sight. It had been months since he’d become stable enough on his prosthetic leg to walk around on his own, so Katsuki’s dig didn’t even make sense.
Not that he had time to consider chasing after him to complain. Power Loader strolled in the door barely a minute later, flanked by his pink shadow. Hatsume immediately locked eyes on the open, separated sole that was pointing up at the ceiling, and zoomed in. When she zoomed back out she was tsk’ing under her breath.
“We were gone a whole hour! I thought you’d have been done with that by now.”
Izuku frowned. Hatsume comparing the speed of their work was comparing a tortoise to a hare.
“I have to start over.” He muttered, putting the closed notebook into one of his pockets and bundling the pieces of his project together to store safely in a locker until the following day. “But it was Kacchan’s fault! He—”
Having planted herself immediately onto a rolling stool, Hatsume zipped to his side. The chair careened into his good leg and nearly toppled him over, but she barely noticed as she picked up the sole and used her quirk to get a closer look.
“Sounds like it was your fault. You should try harder next time!”
After catching himself on the workbench and gaping at the top of her pink hair like a fish out of water for a few seconds, Izuku eventually slumped in defeat. He could do better. But it wasn’t any less painful to hear it from Hatsume, who was beating him in every way possible, than it was to hear it from Kacchan—who was also beating him in every way possible.
“Don’t sweat it too much, Midoriya.” Mr. Maijima was opening a file on his desk and sifting through papers with orange-capped fingers, not bothering to look at his two 1-H students. Between classes, the workshop, and the development studio, he saw entirely too much of them on a day to day basis. “You’ve got nothing but time. Don’t let her discourage you.”
“Yes, sir.” Izuku responded, still sullen as he watched Hatsume set his sole back onto the countertop and roll away.
She was spinning in circles towards Mr. Maijima’s desk while she asked, “How high do you want those to work from, anyway? As of right now they’ll barely clear 100 ft. Just in case you didn’t know.”
“I did know that, but…thanks.”
Gathering his things up in his arms, Izuku made his way over to his locker, trying to keep his tone as neutral and pleasant as possible. It was just…hard sometimes with Hatsume. He thought he was as close with her as anyone was capable of being, considering her brain was hardwired to only think in terms of innovation, but that didn’t really mean too much. She was laser focused on support and her inevitably successful future, while he was fighting tooth and nail just to keep up.
As if he wasn’t also duking it out on 2 other fronts.
“And 4 stories, to start.” He added, locking his project up tight. “Maybe 6 or 8 after I get them working.”
“That’s nice.” She said airily, already pushing herself over to a workstation against one of the walls and promptly forgetting about his existence, and his project, all together. Izuku sighed as he stuck his hand into his pocket.
She was the definition of out of sight, out of mind.
Deciding to follow his homeroom teacher’s advice and to not take her to heart, Izuku went to speak to the man himself.
“Excuse me, Mr. Maijima?” Maijima looked up from his paperwork and hummed under his breath. Taking that as his okay to interrupt, Izuku stuck his curled fist out and opened it to reveal the two destroyed earbuds. “Kacchan brought these back for me to fix because he…well…”
He lifted them slightly and jostled them in his open palm.
“They’re wrecked. Is it okay if I take what I need to repair them?”
Maijima looked a little closer at the two pieces of crushed metal and wiring, then made an affirmative noise and went back to sifting through folders full of change forms for the first year Hero Course students.
“You know the drill. Send me a list of everything you use and I’ll inventory them later.”
Izuku accepted the measure without complaint. Though his year of surveillance had come and gone without much in the way of fanfare, other than little a relief on Maijima’s part at being freed from at least some excess responsibility, he was still expected to catalog every piece he used in the development of his support projects, down to the last bolt.
Shouta was the one pushing for that extra level of detail, though; not Maijima. After watching Izuku in class for a year, his homeroom teacher was confident enough that his second-year student would behave himself. Nezu in particular didn’t care, although Izuku also didn’t doubt the stoat still stalked his hero searches every now and again. And although Shouta was well aware of the fact that Izuku was, in all reality, too busy to be getting himself into trouble, he had no interest in playing games with his son.
He wasn’t going to give Izuku the opportunity to screw up all the hard work he’d put in over the past year.
That was why Izuku didn’t argue the point as he bowed slightly to his teacher and went off to raid the workshop for materials to fix Kacchan’s support gear. He appreciated that Shouta cared enough to keep such close tabs on him, even if most other teens might have been upset at the lack of trust.
Considering that he’d been the definition of untrustworthy…well, suffice to say it was fair enough.
After scrounging up the supplies he needed from the back room at the workshop, Izuku spread his haul out along an open workbench and took stock of everything he’d taken. He’d kept the mold he’d used previously, which was a relief, and the addition of the hook to go around the ear wouldn’t be too much of a hassle to implement. He was fairly confident he could have them done in a day, and definitely could if he stayed a little while after the school day ended.
Though he knew some of his classmates were working in the workshop next door, there was no one with him in the one he’d decided to occupy. So, there was no one else to be scared shitless when the door flew open with the same amount of force as it had in the development studio earlier.
“Did you get the okay?”
“Kacchan!” Izuku half-screamed. His gloved hand dropped the pen he’d been writing with to grip at his racing heart, and his bugged-out eyes watched Katsuki stroll across the room like he hadn’t nearly sent Izuku into an early grave. “You have to stop doing that! What if I was doing something really dangerous, like working with a torch, or cutting something? I could hurt myself, and then—“
“What, you won’t be able to make your nerd shit anymore?”
“No,” There was maybe the tiniest bit of venom in Izuku’s voice when he shot back, “Shouta would make you pay for it in class.”
That shut Katsuki up pretty quick; mostly because he knew it was true. Izuku’s new guardians both being Katsuki’s teachers meant he had to be on his best behavior—or else.
“It’s not fair you have an automatic trump card now.” Katsuki grumbled, not missing Izuku’s triumphant smile as he picked his pen back up and tapped it on the edge of the workbench.
“If you ask me, I think the scales evened out pretty nicely.”
Another pointed silence. Katsuki was already 0-2.
“Whatever.” Moving on completely, Katsuki leaned over the workbench with a skeptical eye. “Is this all that goes in those things?”
Izuku hummed affirmatively and went back to writing. Katsuki didn’t leave. He rested a hip against the edge of the workbench and didn’t say a word, though he definitely noticed from the corner of his eye as Izuku’s pen scribbled, and then slowed, and then stopped.
Izuku blinked in genuine confusion and glanced over his notebook.
“Uhm…Kacchan?”
“What?” Katsuki said shortly.
Izuku’s head tilted.
“You…what are you…is—“ He used his pen to scratch at his hairline. “Is everything okay?”
“Why wouldn’t it be?”
Izuku dropped his notebook slightly and raised an eyebrow.
“Oh, well…I don’t know. You’re just…” In that moment he was hit with a sudden realization. A smirk, quiet and smug, began to creep across his face as he slipped his pen behind his ear.
“Kacchan…did you come down here just to hang out with me?”
It seemed to take a moment for Izuku’s question to process, because Katsuki didn’t immediately respond. When he did finally come to the realization that, yes, Izuku did just imply that Katsuki was bumming around him for fun, his red eyes narrowed, and his jaw tightened.
“Why would I want to hang out with you?” He was holding back a shout with an incredible amount of effort, but his palm still sparked on instinct. He only got more infuriated as Izuku’s grin brightened, his green eyes sparkling. “You’re not the only one who likes to build shit, Deku.”
He threw his head back, a low growl leaving the back of his throat.
“Damnit! Izuku. Just...get over your fucking self!”
“I know!” Izuku’s voice was chipper, even in spite of his irritation, and that didn’t make Katsuki’s fresh scowl lessen any faster. “Your designs are amazing, Kacchan! If you ever want to talk about them, or go over any ideas—“
“Fat fucking chance.” It might have been a more believable stance if he had moved any more than to flex his fingers into his standard pseudo-threatening position. “I don’t need your help.”
Izuku’s face didn’t drop, didn’t lose any of its cheer, as he nodded his agreement of the fact.
“I know, Kacchan.”
Bringing his notebook back up to his face and his pen back from behind his ear, Izuku continued the process of jotting down his inventory for Mr. Maijima. Still, Katsuki stayed. Eventually his hands dropped so he could cross them over his chest. His scowl swapped to a sneer, and then a frown, as he watched.
Izuku didn’t doubt for a second he was trying to put the pieces together in his own head, and the thought made him lift his notebook a little higher to hide a grin.
When he’d finished and stuck the notebook back into his pocket, he didn’t say a word as he started automatically organizing pieces into sections. He could feel Katsuki’s eyes on the components as he slid them across the top of the workbench, one for each ear bud, a process he slowed down maybe a little more than he would have normally.
They were largely silent for the rest of the period. Katsuki’s gaze followed the pieces wherever they went, or Izuku, if he had to travel across the room to use the equipment provided in the workshop. Izuku didn’t complain. It was a quiet camaraderie, more comfortable than any conversation or forced interaction they’d ever had.
Occasionally Katsuki would ask a stiff question, which Izuku would answer enthusiastically; or, the more common case, Izuku would explain what he was doing without prompting. Katsuki wasn’t the easiest to read for most people, but Izuku could interpret the subtle crease of his brow as an unspoken question or general curiosity.
When the bell rang that signaled the end of the school day, Izuku pulled his arm over his chest and stretched. Setting his gloved hands on his hips, fingers tapping at his red utility belt, he finally looked up at Katsuki properly. He was gone.
Izuku blinked a couple of times, gaze flitting over the room, until the sound of metal dragging on concrete made his gaze turn. He was dragging a stool behind him, one he pulled up to the other side of the workbench and threw himself down on. One of Izuku’s green brows quirked up.
“You’re staying, right?” Katsuki asked, once again crossing his arms, one foot tapping almost impatiently on one of the bars that stretched between the legs of the stool. For once he didn’t look angry, or even annoyed, despite his eyes still being narrowed. If anything, there was curiosity in them.
Izuku’s eyes closed as he smiled.
“Yeah.”
“Then get to it, nerd.”
“Right!”
And when Shouta showed up some half-hour later, fully prepared to lecture Izuku for not telling him he planned on staying late, he had to do a double take at the head of spiky blonde hair sitting opposite his kid.
It wasn’t his presence that was that surprising, really. Katsuki was getting better about acknowledging that he didn’t actually hate Izuku, despite his frequent slip-ups into his older, meaner habits. No. It was that Katsuki was currently having a normal, engrossed conversation with Izuku.
He was pointing to pieces and asking questions about how they interacted. Izuku answered eagerly, picking up two and putting them together in demonstration, showing the sketches in his notebook, and gesticulating wildly with his hands.
Any hope of a reprimand dissipated at the sight of the two boys actually getting along. Instead, deciding it might be a once in a lifetime occurrence and worth seeing to believe, Shouta leaned in the doorway, crossed his arms and his legs, and watched.