Etotama

Amato Takeru, a high school student, has just moved to Akihabara. He's chosen a house with cheap rent, but with one particular imperfection: a hole in the living room floor. When he peeks into it, a girl pops out... And so begins the hectic life of Takeru and the cat Eto-musume, Nya-tan. (Source: Crunchyroll)