Junko Hayama, a transfer student, quickly becomes popular among male classmates and considers joining a sports club. Torn between the swimming and gymnastics clubs, she takes advice from her homeroom teacher, Mr. Ishida, and decides to join the gymnastics club. However, Mita from the swimming club grows furious over her decision and conspires with a classmate to ambush and assault Junko in the locker room. Shaken with fear, Junko resolves to quit the gymnastics club, but then suffers further assault by Kawamoto, who mistakenly believes she mocked him and caused the misunderstanding.