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The war was over, but the silence it left behind was often too loud. Perhaps that was why the faculty at U.A. insisted on the heart monitors for the students who had taken the brunt of the final battle.
Katsuki Bakugo, recovering from chest injuries that would have killed a lesser man, was currently tethered to a portable, high-tech monitor. It was a sleek, black wristband that transmitted his vitals to Recovery Girl’s server, but annoying enough to emit a soft, audible chirp if his resting heart rate climbed too high—a safety measure to prevent him from overexerting himself during rehabilitation.
The problem, however, was that the machine was a snitch.
It was a Tuesday evening in the Heights Alliance dorms. Most of Class 1-A was scattered around the common room. Katsuki was sitting on the sofa, a book in his lap, trying to ignore the way his ribs ached.
Beep... Beep... Beep...
The rhythm was steady. A calm 65 beats per minute.
"Hey, Bakugo! Want some popcorn?" Kaminari asked, leaning over the back of the couch.
Katsuki didn't look up. "Choke on it, Dunce Face."
Beep... Beep... Beep...
Steady. Unchanging. The insult was delivered with zero physiological effort.
Then, the front door opened. A gust of wind blew in, followed by a mop of unruly green curls and a scarred hand clutching a notebook.
"Sorry I'm late, everyone!" Izuku Midoriya called out, toeing off his red sneakers. "I got held up talking to All Might about the curriculum changes."
Beep-beep. Beep-beep.
Katsuki’s eye twitched. He gripped his book harder.
Izuku walked into the living area, his eyes immediately scanning the room until they landed on the ash-blonde on the sofa. His face softened into that painfully earnest expression that made Katsuki’s stomach do backflips.
"Kacchan," Izuku said, walking closer. "You’re out of your room? Is your breathing okay today?"
Beep-beep-beep-beep-beep-beep.
The monitor on Katsuki’s wrist began to accelerate rapidly, the soft chirps merging into a frantic tempo.
"I'm fine," Katsuki grunted, looking steadfastly at page 42 of his book, which he hadn't read a single word of in ten minutes.
"Are you sure?" Izuku frowned, leaning in. He was close enough that Katsuki could smell the ozone and soap scent that clung to him. "Your monitor is going really fast. Are you in pain? Do I need to get a cooling pack?"
BEEP-BEEP-BEEP-BEEP-BEEP.
"I said I'm fine, you damn nerd!" Katsuki snapped, pulling his arm away. "Back off!"
Across the room, Mina Ashido nudged Ochako Uraraka. "And... there it is. The 'Midoriya Arrhythmia'."
Uraraka stifled a giggle behind her hand. "It’s getting worse. Yesterday it hit 110 just because Deku asked him to pass the salt."
"It’s painful to watch," Sero sighed, shaking his head. "Everyone knows. Even Aizawa knows. The only person who doesn't know..."
"...is Midoriya," the group chorused in a whisper.
Two weeks passed, and the situation became the unspoken entertainment of Class 1-A. It was scientifically fascinating.
If Kirishima slapped Katsuki on the back? Beep... Beep. (Normal). If Todoroki started a fight? Beep-beep... Beep. (Slight irritation). If Izuku breathed in Katsuki's general direction? BEEPBEEPBEEPBEEP.
Katsuki was living in hell. He knew what was happening. He knew that after the war, after nearly losing everything, the realization of his feelings for the nerd had hit him like a freight train. He was in love with Izuku Midoriya. And because he was currently too injured to blow things up to distract himself, his body was channeling all that repressed emotion directly into his cardiovascular system.
He wanted to rip the monitor off, but Recovery Girl had threatened to tie him to a hospital bed if he tampered with it.
It all came to a head on a rainy Friday night.
The thunder was shaking the dorm windows. The power had flickered out an hour ago, leaving the students in the common room illuminated only by battery-powered lanterns and moonlight.
Katsuki was trying to sleep on the couch because his room felt too stuffy, but the pain in his chest was a dull, throbbing ache. He closed his eyes, focusing on his breathing.
Beep... Beep... Beep...
"Kacchan?"
Katsuki’s eyes snapped open. The room was empty, save for Izuku, who was crouching by the sofa, holding a glass of water.
Beep-beep. Beep-beep. Beep-beep.
"Go to sleep, Deku," Katsuki rasped, his voice rough.
"I heard you groaning," Izuku whispered. He looked ghostly in the dim light, his eyes wide and filled with that terrifying, overwhelming worry. "Is it the scars? Do you need your meds?"
"I don't need—"
"Here." Izuku placed the water on the table and reached out.
Before Katsuki could dodge, Izuku placed his hand gently over Katsuki’s heart, right above the bandages, checking for heat or swelling.
The reaction was instantaneous.
BEEP-BEEP-BEEP-BEEP-BEEP-BEEP-BEEP!
The machine screamed. It was the sound of a heart running a marathon. It was so loud in the quiet room that it sounded like a fire alarm.
Izuku recoiled, panic written all over his face. "Oh my god. Kacchan, your heart rate! It’s skyrocketing! Is it a panic attack? Is it a pulmonary embolism?"
Izuku scrambled for his phone. "I’m calling Recovery Girl. You might be going into shock."
"Don't you dare!" Katsuki grabbed Izuku’s wrist.
BEEP-BEEP-BEEP-BEEP!
"But listen to it!" Izuku cried, his voice pitching up. "Kacchan, you’re physically reacting to stress! Is it me? Am I upsetting you? I know our past isn't great, and I know I annoy you, and my presence probably raises your blood pressure because you hate me being around when you're vulnerable—"
"Shut up!" Katsuki roared.
Izuku froze, mouth open.
"Shut up," Katsuki said again, quieter this time. He was panting, his face burning hot in the darkness. The beeping was a relentless, humiliating soundtrack to his life.
"I don't hate you," Katsuki gritted out, looking away. "That's not why the machine does that."
Izuku blinked, confused. "But... it only happens with me. I've been tracking the data. It’s a direct correlation. Whenever I engage with you, your sympathetic nervous system activates. If it’s not anger or stress, then..." Izuku trailed off, his genius brain hitting a wall because the variable didn't make sense to him. "Then what is it? Are you allergic to my detergent?"
Katsuki stared at him. He stared at the freckles, the messy hair, the sheer, unadulterated density of the man who had saved the world but couldn't read a room to save his life.
"You're an idiot," Katsuki whispered.
"I'm trying to help you not have a heart attack!"
"It's not a heart attack, it's you, you moron!" Katsuki yelled, sitting up despite the protest of his ribs.
Izuku paused. "Me?"
"Yes! You!" Katsuki gestured wildly with the hand wearing the monitor, making the beeping sound like a techno remix. "You come in here with your stupid face, and your stupid concern, and your... your warm hands."
Katsuki grabbed Izuku’s shirt front and yanked him closer. "It’s not anger, Deku."
Izuku’s eyes widened. He was inches from Katsuki’s face now. He searched Katsuki’s ruby eyes, looking for the malice that used to be there, but finding something entirely different. Something terrified and raw.
"Oh," Izuku breathed. The realization hit him slowly, then all at once. His face turned a brilliant shade of red. "Oh."
"Yeah. Oh."
"Kacchan, you..." Izuku swallowed hard. "Does your heart... do this because you like me?"
Katsuki bared his teeth in a grimace that wasn't quite a scowl. "If you make me say it out loud, I will Blast Rush Turbo you through the ceiling."
Izuku let out a breathless, wet laugh. He looked at the hand clutching his shirt, then back up to Katsuki’s eyes. "My heart is doing it too, you know. I just don't have a speaker attached to it."
Katsuki’s eyebrows shot up. "Hah?"
"I... I thought you were just tolerating me," Izuku admitted, his voice trembling. "I've liked you for... well, forever. But I didn't want to push it. I didn't want to ruin how good we’ve been lately."
The beeping on Katsuki’s wrist didn't slow down, but the rhythm changed. It wasn't the jagged spike of panic anymore; it was the heavy, thudding drum of anticipation.
"Well," Katsuki grunted, his voice dropping an octave. "You're not ruining it."
He waited a beat, then closed the distance.
It wasn't a perfect movie kiss. Their noses bumped, and Katsuki winced slightly when he shifted his bruised ribs, but it was electric. Izuku’s lips were soft, and he tasted like the peppermint tea he’d been drinking earlier. Izuku’s hand came up to cup Katsuki’s cheek, his thumb brushing over the sharp cheekbone.
For a moment, the world narrowed down to the contact.
And then, suddenly, the monitor went silent.
Beep............... Beep............... Beep.
They pulled apart, both breathing heavily.
Izuku glanced at the wristband, then at Katsuki, a blinding smile breaking across his face. "It slowed down."
Katsuki slumped back against the cushions, feeling a tension he’d carried for years finally drain out of his body. He looked at Izuku—his Izuku—and huffed a small, genuine laugh.
"Yeah," Katsuki murmured, lacing his fingers through Izuku's. "Guess you're the cure, nerd."
The Next Morning
Katsuki walked into the kitchen to get coffee. The monitor was still on his wrist, beeping a steady, calm rhythm.
"Morning, Bakugo!" Kirishima chirped, eyeing him suspiciously.
"Morning," Katsuki replied calmly.
Izuku walked in a moment later. He walked right up to Katsuki, leaned up, and kissed him on the cheek before grabbing a piece of toast. "Morning, Kacchan."
The room went dead silent. Everyone stared at the monitor.
Beep... Beep... Beep...
It remained perfectly steady.
"WHAT?" Kaminari shrieked, slamming his hands on the table. "No spike? No arrhythmia? Nothing?"
Katsuki smirked over the rim of his mug, wrapping an arm around Izuku’s waist and pulling him close. "I've built up a tolerance."
As the class erupted into chaos—Mina demanding money from Sero, Iida trying to restore order, and Uraraka crying happy tears—Izuku just leaned into Katsuki’s side, beaming.
"Pay up, losers!" Katsuki shouted over the noise, finally, perfectly at peace.
Beep.