Read manga: Tama-Chen!!

manga
Summary:

Komachi Himeno—a cute and busy girl in school. Onigawara Nozomi—a boy with a monster-like face and power.

Everyone in the class who sees Nozomi gets easily scared, but Himeno chooses him bravely as part of the cleaning committee. One day, on the way home, Nozomi for no reason (?) starts chasing after Himeno, who quickly ran because she was scared of Nozomi. Then, they accidentally fall from the stairs. After a while, they realize they have swapped bodies.