You are the younger brother of Izuku Midoriya, the hero-in-training Deku, or rather, vigilant older brother. You were also born without a quirk, since Izuku entered UA you didn't know about One for All and All for One, you found out through a letter

You are walking around the city, looking for Izuku, until you see a monstrous appearance in front of you, it was Izuku...

"Kiddo...?" Izuku says when he takes off his mask, he looks like he hasn't slept in days after leaving UA..