Kirishima didn't mean to hit him that hard.
The training match was supposed to be simple—sparring against Sero, controlled strikes, practicing form. But when Sero lunged, Kirishima's instincts flared.
Too fast.
Before he could think, his body reacted. His arm hardened, the edges sharper, the density stronger, and when he swung—
CRACK!
Sero flew back, his body hitting the mats with a force that stole the breath from the room.
Silence.
Kirishima blinked, his breathing ragged. His knuckles tingled from the impact. Sero groaned, holding his side where the blow had landed. Even with his suit, that had to hurt.
Mina was the first to react. "What the hell, Eijiro?!"
Kirishima took a step back, his heart thudding. He hadn't meant to hit that hard. He was just… reacting. His body had moved before he could tell it otherwise.
Sero winced as he sat up, waving off Mina's concern. "Dude, what was that? You've never hit like that before."
Neither had Kirishima.
He could still feel the sensation in his bones—the force, the impact, like something inside him had been waiting for that moment.
Aizawa's words from the night before clawed their way back into his mind.
"The first time you step outside the rules, it's for the right reasons. But every time after that, it gets easier."
He let out a shaky breath, forcing a grin. "Shit, Sero, my bad. Guess I don't know my own strength."
Sero chuckled weakly, still rubbing his ribs. "Yeah, no kidding."
But as Kirishima turned away, he clenched his fist.
His own strength?
That wasn't just strength. That was something else.
Something new.
And that night, he tested it.
He waited until the dorms were quiet, until the halls were empty. Then, he slipped out and made his way to Gym Gamma.
The room was dimly lit, empty aside from the reinforced punching dummies lined up against the far wall.
Kirishima stood in front of one, rolling his shoulders.
He thought back to the fight with Sero. The feeling before he struck—the way his arm had hardened more than usual, how the force of his hit had been different.
He had felt something. Stored something.
Slowly, he raised his fist.
He tensed, hardening his skin, but instead of striking immediately, he focused on the sensation. The tension in his muscles. The way his body absorbed pressure. The way his bones felt denser, charged.
Then, he threw the punch.
BOOM!
The impact sent a shockwave through the gym. The dummy wasn't just knocked back—it was obliterated, slamming into the reinforced wall and leaving a dent.
Kirishima staggered back, his own body humming.
That wasn't just super strength.
He clenched his fist, feeling the faint buzz beneath his skin.
He had stored it.
Absorbed the kinetic force. Built it up. Then released it all at once.
His breath came fast, adrenaline spiking. This was new. This was different. Had this always been inside him?
He had always thought his quirk was simple. Hardening. Defense. Endurance.
But this?
This was power.
Real power.
And as he stood in the empty gym, staring at the broken dummy, he realized something else.
He liked it.
The next few days, Kirishima couldn't focus. Not in class, not in training, not anywhere. Every part of him buzzed with the memory of the impact, the way his body had taken in the force and released it in an instant.
Had he been limiting himself all this time?
He needed to know more. Needed to push further.
So, he trained.
Late at night, when everyone else was asleep, he snuck out again. Gym Gamma became his hunting ground.
First, he tested how much he could store.
He started by throwing light punches, feeling the way the energy rippled through his bones. Then heavier ones, absorbing the shock each time he struck. Each punch stored a fraction of the force, building in his core like a dam waiting to burst.
Then, he released it.
The walls shook. The dummies shattered. The air cracked with pressure.
Stronger.
Faster.
He wasn't just enduring attacks anymore. He was taking their strength, making it his own.
Noticed
It didn't take long before others noticed.
During class combat exercises, Kirishima's moves were sharper, faster, more aggressive. When he sparred, he hit harder, almost too hard.
Even Bakugo noticed.
One afternoon, after another brutal training session, Bakugo grabbed Kirishima by the collar.
"What the hell's up with you?"
Kirishima blinked. "What?"
"You're different. You're fighting like a damn berserker. Like you're trying to rip people apart."
Kirishima opened his mouth to deny it, but stopped.
Because Bakugo was right.
He had been different. Ever since that night. Ever since he realized what he could do.
Bakugo's red eyes burned into him. "You need to get your shit together. Now."
Kirishima clenched his fists.
But did he?
Because every time he fought, every time he hit harder, it felt right.
It felt natural.
And that was what scared him most of all.