Sakiko, a housewife who lives with her husband, a bank employee, and their son, attends a twenty seven year middle school class reunion. She is there reunited with her first love, Machii Nobuki and accepts his invitation to pay him a visit at the office where he works, only to find him murdered. Gripped by fear, Sakiko flees the scene. Just prior to the police arriving at her home to question her about the incident, she receives a mysterious email from a former classmate and close friend named Hiroe, with whom Sakiko has also just been reacquainted at the reunion party. The peculiar letter was thanking her for a visit which never occurred. Sakiko gives the authorities a false testimony matching what was written in the email, saying that she has paid Hiroe a visit at the time the murder had been committed. However, before long, she finds that Hiroe was betraying her in her actions and the things she was saying.