Katsumi Kunimasa has spent years playing baseball while passing herself off as a boy. After her student team wins the summer tournament, Hoshiyama, manager of the Chunichi Dragons, recognizes her and offers her the chance to turn pro. She joins the Dragons, the club her father owns, and becomes friends with their new catcher, Oikawa. Her pitching gradually wins over the doubters around her. The Dragons players in this sports film are modeled on the real team, while the clubs they face are invented.