Koichi, a student who is preparing to take the entrance exam and lives alone in the same apartment, attends a prep school while working a part-time job. Kanae, who lives next door, sees the hard-working Koichi as somewhat like a younger brother and begins to look after him. However, one day, Koichi fails a mock exam and in despair, he pushes Kanae down. Still, Kanae knows how kind Koichi really is and decides to become his lover for one night to motivate him again... She lies to her husband for the first time.