Imôto no tsubomi: Itazura môsô (2009)

Shinta, a local government employee, 30 years old, a virgin. His younger sister Nana, high school student, 18 years old, definitely ... a virgin. Nobuta, who loves his sister dearly, starts a "virginity club" to protect Nana's virginity. As the queen of the association, she makes the members worship Nana so that her sister will not get any bad bugs. When Nana is about to enter a higher education, Yoshiya, a former school teacher, visits her as a tutor. Convinced that Yoshiya is a virgin, Shinta's mind is filled with agony at the threat of Nana losing her virginity..