Shungo is a normal high school student living in a huge house. One day, his sister Ryoko send two siblings, Mayu and Mikihiro Tsukimura, to live with him so as to help Mayu overcome her problem—androphobia, by making Mayu and Shungo share the same room and bed, and to even take baths together. To make things even worse, Reika Hojo, the student-council chair, somehow ends up becoming their maid.

[Source: Anime News Network]