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He wasn’t sure whether he should be terrified or turned on by Kacchan’s possessiveness. Usually, Kacchan was upfront about his explosive feelings loud, blunt and impossible to misunderstand. If he was angry, the whole room knew it. If he was proud, it showed in the sharp curl of his smirk. But this was different. This was quiet and controlled. Delicate in a way that made Izuku’s pulse stutter every time he noticed it.
They had been secretly dating for a few months now, and it had been nothing short of bliss. Izuku had spent years admiring Kacchan from a distance chasing after him, trying to catch up, trying to prove that he could stand beside him instead of behind him. Now they did stand side by side. Equals. Boyfriends. When Kacchan looked at him now, there was no condescension, no dismissal, there’s heat, respect, and something fierce that belonged only to Izuku. He cherished their secrecy more than he ever expected to. The sneaky kisses stolen in empty hallways. Fingers brushing during training like it was an accident. Late-night visits that started with whispered strategy talk and ended with tangled sheets and breathless kisses. There was something intoxicating about keeping it to themselves, about knowing that the sharpest, strongest person in the room softened only for him.
Still, part of Izuku longed to show him off. He wanted to stand in the middle of the common room and say, Yes, he’s mine. He wanted the world to know that someone as powerful and breathtaking as Kacchan had chosen him, had claimed him just as fiercely in return. Maybe that was why the jealousy had started to feel… complicated.
It had been small at first. Barely noticeable. A subtle tension in Kacchan’s shoulders when Hatsume dragged Izuku off mid-conversation. A sharper tone when he asked how long Izuku planned on staying in the support labs. Nothing dramatic but definitely noticeable. Hatsume had always borrowed his notes on quirk analysis. That was normal. Izuku was more than happy to help. More recently, she’d started insisting he explain things in person. She said she understood concepts better when she could interrupt him with questions, when she could see the way his hands moved as he mapped out hypothetical improvements. Apparently, reading through pages of meticulous observations was “too boring” compared to hearing him ramble excitedly about potential upgrades. Plus it was nice to have someone who was equally as passionate about his hobby, he could ramble on and on without her getting bored. So Izuku had been spending more and more time in the support labs.
He hadn’t thought much of it at first. He liked being useful. He liked feeling needed. Hatsume’s enthusiasm fed his own, and the two of them could spiral into hours-long discussions about gear efficiency and combat applications without noticing the time. Lately, whenever he emerged from the lab, flushed and distracted and carrying a new stack of scribbled schematics, Kacchan would be waiting, he would be watching intensely. Red eyes tracking him with a sharpness that made Izuku’s stomach flip.
Kacchan wouldn’t say anything in front of anyone. He never did. He’d just sling an arm around Izuku’s shoulders. Casual, almost careless and tug him close enough that their sides pressed together. His grip would be firm. Possessive in a way that made Izuku’s breath catch. “Done for the day?” he’d mutter, voice low enough that no one else could hear. Izuku would laugh it off, even as warmth spread across his face.
“We were just discussing support adjustments—”
“I know what you were doing,” Kacchan would cut in. That was the thing. He always knew. The jealousy wasn’t explosive. It wasn’t dramatic shouting or sparks flying. It was controlled heat. A subtle claiming touch. A hand at the small of Izuku’s back. Fingers hooking into his belt loop as they walked. Kacchan standing just a little too close when Hatsume would lean in to show him something on her tablet. It should have annoyed him. It should have worried him. Instead, it made his pulse race. Because beneath the possessiveness was slight insecurity. A new emotion on Kacchan he’s never seen before, it was something raw and stubborn. Mine. Izuku didn’t know how long they could keep this secret. He didn’t know how much longer Kacchan would tolerate watching other people pull at his attention. And if the way Kacchan’s jaw tightened every time Hatsume said “Deku, you’re a lifesaver!” was any indication… The explosion, when it came, wasn’t going to be loud. Izuku wasn’t sure if he was more nervous about that or secretly hoping for it.
It happened on a Thursday. Izuku almost laughed at how ordinary the day had been. Combat training in the morning. A pop quiz in Hero Law. Lunch filled with Kaminari complaining and Iida lecturing and Uraraka smiling at something Mina whispered in her ear. It was all very normal and safe, predictable even. Then Hatsume came storming in, yanking Izuku away without any explanation, already rambling on about her latest idea. Izuku went willingly, not even saying good bye to his friends.
Hatsume had been especially animated, eyes practically glowing as she paced around a half-assembled gauntlet prototype.
“Deku, look, look—if we adjust the internal stabilizers like this, you could output thirty percent more force without shredding your tendons. Isn’t that wild?” she chirped, grabbing his wrist and tugging him closer to the table.
Izuku barely noticed the contact. He was already leaning in, already lost in the schematics.
“If we redirect the recoil through the elbow joint instead—wait, no, that would cause strain during rapid succession attacks. Maybe if we layered—”
They spiraled. Time always slipped in moments like this, of the endless possibilities.
It wasn’t until the lab doors slid open with a soft mechanical hiss that Izuku felt it. He didn’t need to hear it, he could feel it, the shift in the air.
He didn’t need to turn around to know who it was.
Kacchan didn’t slam the door, surprisingly. He just walked in, his boots heavy against the floor.
Izuku’s voice faltered mid-sentence. Hatsume didn’t notice at first. She was too busy waving a screwdriver like a baton. “—and then we test it on maximum output! You’ll probably blow something up, but that’s data, right?”
“Are you almost done ?” Kacchan’s voice cut through the room. His voice low, straining to stay even. Izuku swallowed.
Hatsume finally looked up. “Oh, hey! Perfect timing. I was just stealing your boyfriend for science.”
Silence.
Izuku’s brain short-circuited. She said it so casually and carelessly. Like she’d commented on the weather. Kacchan didn’t react immediately. He didn’t explode like Izuku expected, or jump to deny it. His heart stuttered again, his eyes shifting between the two. Kacchan just looked at Izuku, his eyes sharp and calculating, thinking of the best way to handle her comment. Izuku’s heart slammed against his ribs.
Hatsume blinked between them. “What? I mean, it’s obvious. You hover around him like a guard dog and he looks at you like you hung the moon. I build support gear, I’m not a social idiot, I’m not blind.”
Izuku’s face went up in flames. “H-Hatsume—!”
Kacchan stepped forward, his movements soft for once, he moved with certainty and deliberately. Kacchan closed the distance between them until he was standing at Izuku’s side, close enough that their shoulders brushed. Close enough that Izuku could feel the heat radiating from him.
Then, in full view of the lab—
He slid his hand to the small of Izuku’s back. For once out in the open, firmly and proudly. Kacchan didn’t hide, he was finally claiming him.
“If you’re gonna steal him,” Kacchan said evenly, eyes never leaving Hatsume’s, “ask.”
The words weren’t loud.
But they hit harder than any explosion.
Hatsume’s grin widened. “Ooooh. Territorial. I like it.”
Izuku could barely breathe. Kacchan’s thumb pressed slightly into his lower back. Grounding him back into reality, Kacchan’s hold on Izuku was very possessive, the jealousy in his eyes simmering down until disappearing completely.
“I wasn’t stealing him,” Hatsume added with a shrug. “Just borrowing. He likes talking shop with me.”
Kacchan’s jaw tightened.
“I know he does.”
There it was again, finally so reassuring. No more insecurities, or lingering doubt.
Izuku felt something shift inside his chest.
All this time, he’d thought the jealousy was simmering toward something sharp. Something dangerous. But standing here now, with Kacchan openly touching him, openly staking his place.
Izuku’s fingers moved before he could overthink it. He reached back and caught the edge of Kacchan’s sleeve, holding on.
Not because he needed reassurance but because he wanted to. Kacchan’s eyes flicked down to the gesture and he softened. Just barely but enough for Izuku to notice.
“I’m almost done,” Izuku said quietly. To him. Not to Hatsume.
Kacchan hummed in acknowledgment.
“Five minutes.”
His voice more firm, it was clear in his eyes that he wanted more alone time. Hatsume waved them off with exaggerated annoyance.
“Fine, fine. Take your dramatic tension somewhere else. But Deku, you’re coming back tomorrow. We’re not done breaking physics.”
Izuku laughed, nerves finally loosening. “I will.”
Kacchan didn’t look happy about it but he didn’t argue. He didn’t want to stop Izuku from being passionate or for being needed. He just needed the world to understand one thing. That Izuku was his, and no one else’s. It didn’t matter who or what tried to come between them, he’d always be beside Izuku, and nothing would ever change that.
When they stepped out into the hallway, the door sliding shut behind them, Kacchan’s hand didn’t leave his back. It slid lower, he hooked into his belt loop. Pulling him as close as possible.
“You really that dense?” Kacchan muttered.
Izuku blinked up at him. “About what?”
“About how you look when you’re excited.”
His breath caught.
“How I look?”
“Like you’re in love with whatever’s in front of you.”
His words were soft, creeping into a different emotion, his eyes flickered over his face and displayed an emotion Izuku wasn’t ready for. They were vulnerable. Izuku’s heart stuttered.
“Kacchan,” he breathed, stepping into him instead of away. “I am.”
Red eyes flashed.
“Yeah?”
He nodded. The silence between them thickened. Kacchan’s hand tightened, just slightly.
“Good,” he said.
This time when he leaned in, it was brief, soft and intentional. Anyone could have turned the corner and seen. Izuku’s fingers curled into Kacchan’s shirt. Maybe the explosion wasn’t meant to destroy anything.
Maybe it was meant to make something undeniable. For the first time since they’d started keeping secrets, Izuku wondered maybe he didn’t want it to be a secret anymore.
Lunch was loud and chaotic. It always was. The cafeteria buzzed with overlapping conversations, trays clattering, Kaminari laughing too hard at something Sero said while Mina was being fed fries off Kirishima’s plate. It was normal. Izuku should have known he wouldn’t survive it unscathed.
He’d barely sat down when Mina leaned across the table, chin propped in her hands, eyes sparkling with something dangerous.
“So,” she sing-songed.
Izuku froze mid-bite. “S-So?”
Ochaco leaned in from beside her, trying and failing to hide her grin. “You’ve been spending a looooot of time in the support labs lately.”
Kaminari’s eyebrows shot up. “Ohhhh. Lab partner romance?”
“It’s not like that!” Izuku squeaked immediately, nearly choking on his rice.
“Sure,” Mina said sweetly. “Working.”
Kirishima leaned forward, resting his elbows on the table. “Hey, if you’re into her, that’s cool! She’s intense, but that’s kinda your type, right? Passionate, driven.”
Izuku blinked. “My type?”
Iida adjusted his glasses with a precise motion. “If I may offer an objective observation, Midoriya, you and Hatsume do exhibit a high degree of compatibility in terms of enthusiasm and intellectual synergy.”
“That’s not helping!” Izuku groaned.
Ochaco nudged him gently. “She says ‘Deku, you’re a lifesaver!’ like, every time she sees you.”
“That’s just how she talks!”
“And you light up when she asks you about the improvements you were working on,” Mina added. “It’s cute.”
Across the table, Kacchan hadn’t said a word. But he was eating almost too quietly. Which, in itself, was concerning.
Izuku could feel it even without looking, heat simmering just beneath the surface. Not explosive. Not yet.
Kaminari grinned wickedly. “You should just ask her out.”
Silence fell for half a second.
Izuku’s chopsticks clattered against his tray. “W-What?!”
“Yeah!” Sero chimed in. “Go for it, man. Worst she can say is no. Or ignore you because she’s building something.”
Mina clasped her hands together dramatically. “Ooooh, imagine it. Deku and Hatsume. Power couple of the future.”
Izuku was going to combust.
“I’m not— We’re not— It’s not like that!” he insisted, hands flailing helplessly.
Kirishima laughed. “C’mon, bro. You deserve someone who matches your energy.”
“That’s not—” Izuku sputtered.
“Midoriya,” Iida interrupted, earnest as ever, “if you harbor romantic feelings, it is best to express them clearly and respectfully. Secrecy can lead to misunderstandings.”
The word secrecy landed like a dropped weight. Izuku’s stomach flipped. Across from him, Kacchan’s chopsticks snapped. The sharp crack cut through the table chatter.
Everyone stilled. Kacchan set the broken wood down carefully.
“Ask her out?” he repeated.
His voice wasn’t loud. It didn’t need to be.
Mina blinked. “Uh… yeah? If he likes her?”
Kacchan didn’t move. But something in his posture shifted. Tighter.
“You wanna ask her out?” Kacchan asked.
It wasn’t directed at the group. It was for him.
Izuku’s heart hammered. “K-Kac— I mean— I don’t—”
The table leaned in. This was the moment where he usually deflected. Laughed it off. Let the teasing roll over him. But Kacchan was watching him. If he was angry or upset it didn’t show, he masked it well so he was just waiting.
Izuku swallowed. “I don’t want to ask her out.”
Mina frowned. “You don’t?”
“No!”
“Then why are you blushing every time we mention her?” Kaminari teased.
“Because you’re all staring at me!”
Sero smirked. “So there’s no one you’re interested in?”
Izuku’s mouth opened. Closed.
He could feel Kacchan’s gaze like a physical thing against his skin. Heat crawled up his neck.
“There is,” he admitted softly.
The table erupted.
“I KNEW IT!”
“WHO?”
“Midoriya, you sly dog!”
Ochaco’s eyes went wide. “Wait—really?”
Kacchan didn’t move. But something in his posture tightened.
“Who is it?” Mina demanded, practically vibrating. Izuku’s pulse roared in his ears.
He could lie or maybe he could dodge.
He could keep their secret safe and small and tucked away where no one could touch it.
But—
He’d wanted to stand in the middle of the room and say it.
Sero grinned and threw an arm around Izuku’s shoulders. “If it’s not Hatsume, then who? C’mon, man, give us a hint.”
That was it, the final straw that broke Kacchan’s composure. Kacchan stood up, carefully and quietly.
The scrape of his chair against the floor was sharp enough to silence the entire table.
He didn’t shout or make a scene, he didn’t need to slam his hands down. He just reached out. Grabbed the front of Izuku’s uniform and tugged him forward. Gentle in the way Izuku was now used to, his hands just as careful as he usually is. His grip firm enough that Izuku stumbled half out of his seat, catching himself against Kacchan’s chest. Gasps rippled around them.
Kacchan’s hand stayed fisted in Izuku’s collar. His other hand came up and settled at Izuku’s waist. Solid and possessive just like back in the labs. He leaned down and captured Izuku’s lips in his, for a brief moment, but long enough to make a point.
“Mine,” he said.
The word was low and perfectly clear, unmistakable. The cafeteria felt like it tilted. Mina’s jaw dropped. Kaminari’s mouth formed a perfect O. Ochaco’s hands flew to her mouth. Kirishima blinked. “Bro.” Sero choked on his drink.
Izuku’s brain stopped functioning.
“K-Kacchan—” he breathed.
Kacchan’s grip tightened slightly, pulling him closer instead of letting go.
“He’s not asking anyone out,” Kacchan continued, eyes daring anyone to challenge him. “He’s not available. He’s not interested.”
A beat.
“He’s mine. No one else’s.”
The words settled heavy and undeniable over the table. For half a second, no one moved. Then—
Mina shrieked. “FUCKING FINALLY!”
Ochaco squealed, half laughing “You guys are dating?!”
Kaminari slapped the table. “There’s no way you kept a huge secret like that!”
Kirishima’s grin stretched wide. “That’s so manly!”
Iida straightened abruptly. “You two were concealing a romantic relationship from your classmates?!”
Izuku could barely process the noise. Because Kacchan was still holding him. Still looking at him. Not at them. Not anywhere else.
There was something vulnerable there now. Exposed. Like he’d stepped off a ledge without knowing if Izuku would catch him.
Izuku’s embarrassment melted into something warm, becoming more fierce. He curled his fingers into the fabric of Kacchan’s shirt, stabilizing himself back into the moment. He didn’t want Kacchan to get the wrong idea, like he wasn’t claiming him back.
Once everyone got over their shock completely, Mina launched herself across the table to hug them both at once. Kaminari demanded details. Sero started chanting “How long? How long?” Kirishima looked absurdly proud. Ochaco beamed through watery eyes.
Through all of it Kacchan didn’t let go. Not until Izuku squeezed his hand first. And even then, his fingers lingered at Izuku’s waist like a silent reminder. Just a claim he made openly, finally. No more secrets.
It felt like relief, stepping into the light and letting everyone see the real him. The world felt brighter. And when Kacchan leaned down just enough for only him to hear, voice rough but steady—
“Guess we’re public now…”
Izuku smiled brightly and clung on tighter.
Kacchan’s room felt different that night. Maybe it was just Izuku. The door had barely clicked shut before Izuku was laughing again—breathless, disbelieving laughter that kept bubbling up like he couldn’t hold it in.
“We really did that,” he said, dragging a hand through his curls. “You just—you just said it. In front of everyone.”
Kacchan leaned back against his desk, arms crossed, trying and failing to look unaffected.
“Tch. They were being annoying.”
Izuku grinned. “So you claimed me in the cafeteria because they were annoying?”
A faint flush crept up Kacchan’s neck. “I claimed you because they were talking about you like you were available.”
The word hung between them. Available. Izuku stepped closer.
“I wasn’t.”
“I know that.” Kacchan’s eyes softened, just slightly. “But they didn’t.”
There it was again, warming Izuku all over his body and down to his toes. Certainty.
Izuku stopped right in front of him. Close enough that their shoes bumped.
“You didn’t even hesitate,” he murmured.
Kacchan huffed. “I hesitated for months.”
That startled a laugh out of Izuku. “You did not.”
“Idiot,” Kacchan muttered, but there was no bite to it. “You think I didn’t notice how you looked at me before we started dating? You think I didn’t think about what would happen if we went public?”
Izuku blinked. Kacchan uncrossed his arms, one hand coming up to hook into the fabric of Izuku’s sleeve.
“I just… didn’t want them looking at me different. Or treating me different because of who I like.”
The confession was quiet. Rough around the edges. Izuku’s chest tightened. Knowing Kacchan he wouldn’t want to linger in the raw emotions so Izuku laughed under his breath. “You know Mina’s going to demand a full relationship timeline, right?”
“She can try.”
“And Kaminari is absolutely going to call you ‘soft’ for the next three weeks.”
“I’ll blast him.”
“You won’t.”
“…Probably not.”
Silence settled comfortable and warm.
Izuku’s hands found their way to Kacchan’s sides, fingers curling lightly into his hair.
“I liked it,” he admitted.
Kacchan’s gaze sharpened. “Liked what?”
“You saying I was yours.”
The air shifted. Kacchan’s hand slid from Izuku’s sleeve to his waist familiar now, natural. Not hidden.
“You didn’t look very certain,” he said carefully.
“I wasn’t.” Izuku leaned in just enough that their foreheads brushed. “But I realized all I’ve wanted is to show you off.”
A small, stunned pause.
“Show me off?” Kacchan repeated.
Izuku hummed. “Do you have any idea how cool you are? How strong? How—how incredible?” He smiled sheepishly. “I kind of love that everyone knows you chose me.”
Something fierce and tender flickered across Kacchan’s face.
“They know you chose me too,” he said.
Izuku’s breath caught. Kacchan’s thumb brushed slowly along his waist, grounding. “You stood there. You could’ve backed off. Could’ve said it was a joke.”
“I wasn’t going to.”
“Yeah.” His voice dropped softer. “I should’ve figured.”
For a moment, they just stood there no teasing, no explosive temper, no secrets pressed between them. Just warmth. Kacchan leaned down first this time. The kiss was slow and soul-warming. Izuku melted into it with a quiet hum, fingers tightening slightly in Kacchan’s hair as if to anchor himself there.
When they pulled apart, they didn’t go far.
“So,” Izuku said, smiling against his mouth, “does this mean I can sit next to you at lunch without pretending it’s random?”
“You’re sitting next to me,” Kacchan replied immediately.
“And hold your hand?”
“If you want.”
Izuku’s eyes sparkled. “I do.”
Kacchan huffed softly but his fingers laced with Izuku’s without hesitation. No more hiding or sneaking around. They could just be.
Izuku rested his head against Kacchan’s shoulder, their fingers still linked between them.
“You’re mine too, you know,” he said softly.
Kacchan’s arm came around him without hesitation.
“Yeah,” he replied.
“I know.”