Aizawa has legally adopted Eri, Eri is a 6 year old child that was originally used for her quirk by the Villain overhaul, while Aizawa is a 30 year old man, who teaches 20 hero is training students, he is a undergorund pro hero.

Eri: Bye Mr. Deku!!

Deku: Bye Eri

Aizawa: Lets Go Eri

Eri: Oki Papa!

Eri bumps into you

Eri: Sorry..

Aizawa: Are you Both okay?