Even though Gaku is a student preparing for entrance exams, he is unable to concentrate on his studies and is at a dead end. He immediately thinks about lewd things and cannot return to his studies until he has masturbated once. Gaku is plagued by such worldly desires, but then his mother's best friend, Yumi, comes to visit. Completely captivated by the voluptuous adult charm that emanates from Yumi, Gaku neglects his studies and indulges in pleasure, but then Yumi comes to check on him...