Koichi is an adult exam retaker who lives alone in Kanae's apartment building, working part-time while attending an exam prep school. He reminds Kanae of her younger brother, so the married woman begins looking after him. After failing a practice exam, a distraught Koichi loses control and pins her down. Knowing that he is truly kind at heart, Kanae decides to become his lover for one night and help him regain his motivation—even if it means telling her husband her first lie.