Za kyokuchi

Original title: ザ・極致

Directed by Minoru Matsui

A high school girl who lives with her newlywed sister and her husband. She masturbates every day, becoming frustrated by the extreme sex voices of her older sister and her husband. Her energetic sister is not satisfied with just her husband, and she also has an affair with a salesman. Her sister sees this and seduces her sister's husband without telling her sister...