Rito, Becomes a Woman

As Saruyama tries to explain about boobs to Rito, the girls including Lala overhear the conversation. Lala asks for more facts about boobs and gets the idea that all men are interested in breasts. She makes an invention that will make her boobs the perfect size, but Rito flies out from a school window and crashes into the invention, turning him into a girl.

Synopsis excerpt via Kitsu.