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Zero: The Birth of the World's Best Hero Duo

Chapter Text


His mother turned around in the living room, startled. At the look on his face, she set down the All Might cartoon next to the TV.

Katsuki could feel Zuku fidgeting next to him.

“What is it, Katsuki?”

“Why…why do we live with Zuku? With Zuku and Auntie?”

His mother sighed. “Inko and I have been friends for a very long time, Katsuki. You know that.”

“It’s weird.” Zuku stepped closer to his side. He squeezed his friend’s hand. He didn’t think it was weird.

Another frown. “Why do you say that?”

“Everyone says that.” Bunch of jerks.

His mom was walking toward them and kneeling down, now. “And who is this everyone, brat? I don’t say that. Your Dad and Auntie don’t say that.”

“At the park.” Zuku’s quiet voice spoke up. “They laughed at us. But Kacchan yelled at them.”

“I see.” She stayed there, just watching them. Katsuki frowned. Why wouldn’t she answer? He was about to yell at her, but his mom started to stand up, “I suppose you two are almost four, and we can't keep hiding this from you forever. Let me go get Inko and your father, Katsuki. They should be here.”

Katsuki didn’t understand. Hiding what? And all the adults? Everyone was usually here for dinner and shit, but Auntie always had to leave right after. She had to go to work.

“Why wake up Mom? Mom needs sleep. We have to be quiet before dinner. Mom sleeps then. But Auntie said she was getting Mom. And getting your dad. But your Dad’s usually awake now. Why get both? This—”

“Oi.” Katsuki whacked Zuku on the back of his head. “Stop it. They’ll tell us soon. You wanted to know, too, right?”

Deku nodded.

“Tch.” Katsuki was about to scold him for looking so shitty and weak, but then his mom came back. This time with his dad and Auntie. Auntie looked really tired. He frowned.

Auntie sat down on the floor in front of them. “You know those two water heroes you boys like?”

“Yeah!” Zuku grinned, suddenly not worried. “The water horse duo!” He was bouncing up and down now. The nerd loved heroes. “They’re soulmates! So they work really well together! And they’re super strong!”

Auntie smiled. “Yes, they are very lucky. Not many people find their soulmates.”

“They’re awesome!”

Katsuki was confused. Why were they talking about the stupid water heroes?

Auntie just kept going, though. “How did they know they were soulmates?”

“The signs!” Zuku was still bouncing, happy to answer any question about a hero.

“Good job.” Auntie was smiling at them both. “And what are the signs of a soulmate?”

“Um….” Zuku frowned. “You have to be near them? At least at first. And…they’re perfect for you! And…” The frown deepened.

“There’s a mark.” Katsuki glared at the Midoriyas. He just wanted his question answered. He didn’t understand why they were talking about this. “And after the mark, you start feeling their crappy emotions and pain and shit.”

Auntie sighed at his language, but she didn’t say anything.

“Yes, Katsu-kun. When soulmates complete their bond, a mark that represents them appears on their chests. And then whenever a situation is bad, they can feel the other’s emotions and pain.”

“And Shield felt his soulmate’s location! And Ghost her soulmate’s thoughts! And—”

“Yes, Izu-kun,” She ruffled Zuku’s ridiculous hair. “It can be different for everyone.”

They sat in silence.

More silence.

Katsuki couldn’t take this anymore. “Why do we live together?!?!” He glared at the three adults. He just wanted an answer!

His mom glared back, “Katsuki, you and Izuku are soulmates.” She growled in annoyance, “I almost feel sorry for the boy, being stuck with a brat like you forever.”





“Only adults have soulmates.” He glared at them. “Lying is mean.”

He turned to Auntie, maybe she would tell him. But she still had that same smile. “It’s true that people don’t usually find their soulmate until they’re at least 16, if at all, but you and Izuku are very special, Katsuki.”


Of course he was special.

But Zuku?

He and Zuku were…

Zuku was just sitting there, but a huge smile was beginning to form. “Isn’t that great, Kacchan!” Suddenly Zuku was clinging to him, shaking him back and forth. “Kacchan, Kacchan, soulmate pairs are great heroes! We’re gonna be like that!”

“Tch.” Katsuki tried to pry Zuku off but couldn’t. Stupid nerd had glue fingers. “We’ll be the best, Zuku. Not great! I already said that!”

“But it’s like, for sure, now! Because soulmate hero duos are the best! Everyone knows that!”

Katsuki’s dad kneeled down in front of them, right next to Auntie. At that, Zuku quieted down. Katsuki’s dad didn’t talk to them too much, unless it was serious. “Katsuki, do you know why we live together, now?”

Why they…?



“Zuku and I can’t be apart, can we?” He’d never… never actually thought about it. But he couldn’t remember EVER being more than a few feet away from Zuku. Sometimes they were in different rooms, but that was it. Zuku was just… always there.

And leaving him….

He winced. Crap, even the thought hurt. Ok, maybe his parents were right.

“No, son. You can’t. You two met when you were still babies, and when we tried to take you home that evening…” He sighed. “Both you and Izuku got high fevers before the night was over. When we took you to the doctors, no one could fix it. But thankfully they transported you both to the same hospital, and since you seemed to have gotten it at the same time, they put you in a room together…”

His dad sounded sad. Katsuki didn’t like that. “We got better. We got better together.” That’s what would happen if they were really soulmates.

“Yes.” Auntie was crying, hugging his mom. Shit. Had it been that bad? “When the same thing happened a second time, we put two and two together and took you to a specialist.” His dad ran a hand through his hair, then checked to make sure that he still had both of their attention. “The specialist is the only one outside of the family who knows, boys. And it needs to stay that way. Do you know why?”


Shit, damn, crap, shit.

Katsuki didn’t like this. “Villains hurt soulmates. It’s easier than hurting the hero.”

“Exactly.” He patted their shoulders, “You two are going to be strong one day, and you can decide whether to tell people then, but until that time you need to keep this a secret. If people know now, and one of you becomes a hero, all a villain will have to do is find an old classmate or teacher and threaten them and suddenly they’ll know your soulmate.”

And now Zuku was crying. “I don’t wanna get hurt! I don’t wanna hurt Kacchan!”

Katsuki pulled the nerd into his lap, hugging him. No one would hurt him. Ever. “And you won’t. We won’t tell anyone. Everything will be ok.” Shit. He was still crying. “We’re going to be the best heroes, right?”

“Right!” Sniffles.

“So no one will hurt us.”

Slower sniffles. “You’re right, Kacchan. You always are.”

“Damn right, I am.”

Katsuki’s dad whacked his head. “Enough of that language, brat.”