Dana's manga / #School Setting(1)

1,6 - three masked guys fell inlove with the same guy and raped him 2 - story of twins (boy &girl), the male twin loved their male friend whom he thought loved his twin sister and asked him to be a substitute for his twin sister in exchange for the male friend's body (plot twist: the male friend actually liked the male twin and used the twin sister to make him jealous)