Imôto no tsubomi: Itazura môsô.

Worried about Nana's poor grades as graduation approaches, her parents decide to hire a live-in tutor. The tutor they hire is Misato's older brother, Nomura Yoshiya, whose cram school has gone bankrupt. Yoshiya's arrival causes a small ripple in the Ooe household. Nana falls in love with Yoshiya at first sight, and Yoshiya seems quite pleased with her. Seeing this, Nana's brother, Shinta, becomes increasingly uneasy. Shinta subtly tries to find out more about Yoshiya, only to discover that he currently has no girlfriend, and despite his handsome looks, he has an old-fashioned desire to give his virginity to his future wife…