Karin Kiritani is a third-year student at Tokyo Metropolitan Hoshizakura High School who yearns to go to Koshien. She is a pitcher on the girls' baseball team, but is beaten by Mirei Hiiragi in the spring tournament. Under the guidance of her childhood friend Daimon Rai, Karin tries to improve her pitching form and grip on the ball, but will she be able to beat Mirei?