Author's Note: I'll be publishing seven oneshots this week for Dad for One Week 2021 (see dad-for-one-week on tumblr). Day One prompt: Take Your Child to Work Day.
All Might had been hunting All for One, the villain who murdered his teacher, ever since his return to Japan. His big breakthrough happened entirely by coincidence. Detective Tsukauchi received a tip about a deal to swap two villains' quirks. It was only a rumor, but All Might had no other leads.
He leapt from rooftop to rooftop, finally dropping down on top of a skylight. Through the glass underneath him, he saw two villains speaking to a man with curly white hair. All Might's jaw clenched. He'd know that smug smile anywhere.
"All for One!" All Might roared as he broke through the skylight, determined to defeat his fated nemesis and avenge Nana.
The two minor villains took one look at the Number One Hero and fled.
All for One turned around with an annoyed look on his face. All Might screeched to a stop, his fist still raised, as he realized that his archnemesis had a baby carrier strapped to his chest.
"Ah-Ma! He-ro!" The green-haired baby waved his arms and giggled. His features looked uncannily like All for One's, right down to his freckles.
All Might pointed. His mouth opened and closed. After a moment, he finally said, "What?"
All for One sighed. "My wife couldn't find a babysitter so I had to take my son to work with me. I'm afraid I can't fight you today. I need to leave now if I'm going to drop him off at daycare on-time."
"Stop right there!" All Might glared. "Of course I'm not going to just let you leave, villain."
All for One raised an eyebrow. "What, are you going to murder me in front of my baby son?"
"Well…I…" All Might fell into a state of contemplation and moral uncertainty.
"Just look at those cute green curls and freckles." All for One held up his infant son. "I dare you to look him in the eye and say 'I'm about to kill your father and make you watch.' What kind of hero are you?"
All Might stared into those adorable green eyes with white pupils. How could the physical manifestation of evil possibly have produced such cuteness? It was inconceivable. "I guess we could fight another day."
While his enemy was distracted, All for One shot forward a spike and stabbed him in the gut.
As All Might gurgled on the floor, All for One laughed manically. "Serves you right for getting distracted, hero!"
"Bad Dadda!" the baby cried. "No hit Ah-Ma!" He beat his father's face with his tiny fists.
All for One reeled away from the blows. "Shhh, Izuku. I'm sorry I scared you." His foot slid in a patch of blood. He fell over backward.
As All for One landed on the floor, All Might reached over and ripped his face off.
While in the hospital and high on painkillers, the one thing both enemies mutually agreed upon was that they would never speak of this again.
OMAKE TIME!
Omake: The True Cause of All Might and Sir Nighteye's Fallout
Sir Nighteye: I'm so glad you're alive. I wish I'd predicted this so I could have helped you avoid your injury.
All Might: Don't let it concern you, Mirai. You can't know everything.
Sir Nighteye: Last time I touched you, all I got was a ridiculous vision where All for One distracted you with a baby and then got beaten up by the same baby.
All Might: WHAT.
Sir Nighteye: It was so silly, I didn't consider it worth sharing with you.
All Might: Why you useless bastard—
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Omake: The Denial Continues Throughout Canon
All Might: I've decided to make you my successor, kid. What's your name?
Izuku: I'm Izuku Midoriya.
All Might: (Beat.) What an amazingly coincidental coincidence!
Izuku: It is? Do you know another Izuku?
All Might: I've never met anyone with that name before in my entire life.