Junior high school teacher Yuko Moriguchi (Takako Matsu) announces to her class that she will resign before spring break. Moriguchi reveals that because the HIV-positive biological father of her daughter Manami was ill, she used to bring Manami (Mana Ashida) to school with her. One day, after school, she returned to the room where Manami was but found her gone. Her daughter was later found drowned in a school swimming pool. She then explains that two pupils in her class, whom she dubs "Student A" and "Student B", have murdered her four-year-old daughter.
