Jin Tomari, a first-year high school student on the track and field team, and Seiko Moriyama, who is also on the same track and field team, thought they were just friends. When she learns that Jin's best friend, Seko, has confessed her feelings to Seiko, she feels for the first time that she is not just her friend, but a woman. Although Seiko is worried about her relationship with Jin, she decides to go out with Seko...!!