One week after Bakugo's birthday, Katzo found himself sitting in a sterile clinic waiting room.
Inko had brought both Izuku and Katzo along for Izuku's annual checkup. "It's just a routine visit," she'd said, smiling. "They'll check his Quirk status now that he's four."
Katzo had frozen when he heard that.
Quirk status. Doctor.
His mind raced through his memories of the manga. There was only one doctor in Mustafu that mattered — the one who told Izuku he was Quirkless. The one who worked for All For One.
Dr. Garaki.
"Katzo? You look pale." Inko touched his forehead. "Are you feeling sick?"
"No," he said quickly. "Just… which doctor is this again?"
"Dr. Tsubasa," Inko said. "He's very good with children."
Tsubasa. That's him. That's Garaki's alias.
The door opened. A man with glasses, a lab coat, and a too-friendly smile stepped out. "Midoriya family? Right this way."
Katzo grabbed Izuku's hand.
"Hey — what are you doing?" Izuku blinked.
"I don't like this place," Katzo whispered. "Let's go somewhere else."
"But Mom said —"
Inko looked back, confused. "Katzo? Come along."
They entered the exam room. Dr. Garaki — Tsubasa — had Izuku sit on the paper-covered bed. He asked questions. Took notes. Smiled that awful smile.
Katzo stood in the corner, heart pounding.
I can't prove anything. He hasn't done anything wrong yet. But I know. I KNOW.
When the doctor reached for a needle to take a blood sample, Katzo stepped forward.
"Auntie Inko," he said, tugging her sleeve. "I don't feel good. I think I'm gonna throw up."
Inko's eyes widened. "Oh! Right now?"
"My stomach hurts really bad." He made his face pale — not hard, since he was genuinely stressed. "Can we go home? Please?"
Izuku looked worried. "Maybe we should go, Mom."
Dr. Garaki's smile tightened. "We're almost done. Just a quick —"
Katzo fake-gagged.
Inko scooped him up immediately. "I'm so sorry, Doctor. He's been through a lot — the accident, you know. We'll reschedule."
She rushed both boys out. Katzo buried his face in her shoulder, breathing easier the farther they got.
---
In the car, on the way to the second clinic.
Izuku was quiet for a moment, then whispered, "Katzo, were you really sick?"
"No," Katzo admitted, voice low so Inko couldn't hear from the driver's seat. "I just didn't trust that doctor."
"Oh." Izuku accepted that without question. Then his eyes lit up. "Did you see Kacchan's Quirk the other day? When it exploded?"
"Yeah. Little sparks."
"It's going to be so cool when it gets bigger. Don't you think?" Izuku's hands mimed explosions. "Boom! He'll be able to fly and everything."
Katzo snorted. "Fly? He'll just be loud and smell like burnt sweat."
"Still cool!"
"I guess." Katzo leaned his head against the window. "What do you think your Quirk will be?"
Izuku's face fell slightly. "I don't know. What if I don't have one?"
"You have one," Katzo said firmly. "I can feel it."
That was a lie. But it made Izuku smile.
---
Later that day, a different clinic.
Inko found a small family practice two neighborhoods over. A kind older woman with gray hair examined Izuku while Katzo sat in the waiting room, finally calm.
The doctor came out with a puzzled expression.
"Mrs. Midoriya," she said, "your son has a Quirk."
Inko gasped. "But the other doctor — we never got the results from —"
"It's dormant. Very dormant. I almost missed it." The doctor showed her a scan. "See here? His toe joint is single-jointed, not double. That indicates a Quirk factor is present. But it's not active — like a seed waiting to sprout."
Izuku's eyes went wide. "I… I have a Quirk?"
"Technically, yes. It may never manifest strongly, but it's there. I'd recommend checking again when he's five or six."
Inko cried. Izuku cried. Katzo smiled from his waiting room chair.
One butterfly flapped its wings, he thought. Dr. Garaki didn't get to label him Quirkless. Who knows what happens now?
---
On the drive home, Izuku wouldn't stop talking.
"I have a Quirk! A real Quirk! It's dormant but that means it's there! Kacchan has his explosions, and I have something — what do you think it is, Katzo? Maybe super strength? Or something with fire? Or —"
"I think," Katzo said, cutting him off with a grin, "you need to calm down before your brain explodes."
Izuku laughed. "But this is the best day ever!"
Inko wiped her eyes in the rearview mirror. "It really is, sweetie."
Katzo looked out the window, watching the streets of Mustafu pass by. He thought about Bakugo's Quirk — those small sparks that would one day become something terrifying.
Explosion. Katsuki secretes nitroglycerin-like sweat from his palms and ignites it. Right now it's weak. But you know what it becomes. Blasts big enough to launch him across a battlefield. Mobility, firepower, intimidation.
And someday, maybe you'll copy it.
If you're lucky.
If the mutation doesn't ruin everything.
He glanced at Izuku, who was still bouncing in his seat.
Or maybe I'll copy whatever he ends up with.