Sister Scheme: Oneechan to no Shikata ni Tsuite  

しすたー・すきーむ～お姉ちゃんとのシかたについて～

Anjou Sakito, a typical high school student, harbors feelings for Kusaka Isami, a classmate and president of the public morals committee. His sibling, Anjou Marine, is also infatuated with him. During a conversation at school, Anjou Marine became sexually aroused and subsequently masturbated in the restroom. Later that day, she received a letter containing an image of this act along with directives to avoid the dissemination of these photos. The initial instruction required Sakito to capture a photograph of himself embracing his sister near the school's entrance.