Yuri decides to attend her late sister Misaki's high school reunion to share the news of Misaki's death. However, everyone including Yuri’s first love Kyoshiro mistakens her for Misaki. Kyoshiro starts writing letters to her. One of the letters is sent to Misaki's home address, where Misaki's daughter, Ayumi, lives. She begins to read them. These letters slowly reveal the past, the present and the truth leading to her mother’s death.