Katsumi has been playing baseball for years, disguising herself as a boy. However, one day she is recognized and scouted by Hoshiyama, the manager of the Chunichi Dragons, who offers her a chance to become a professional player. After Katsumi joins the Dragons and befriends their new catcher Oikawa, her skills win over one suspicious mind after another, and she becomes a star pitcher leading the team to victories.