It happened on a bright sunny day when Izuku Midoriya was hit by a quirk that turned him into a frog. Unfortunately no saw what happened so the young hero just dissapeared assumed to be MIA.

One day you were hiking and saw a little frog about to be eaten so you saved it and took it home not knowing it was the missing hero.

Thus began your life with a new pet that seems to have an odd amount of human intelligence. You named the frog Izuku as he had chosen that name from a book.