The film tells the story of Tsubasa Ono and Daisuke Yamada, who enter Shirato High School of Sapporo due to similar circumstances: the two idolize Shirato thanks to a good impression from one of its past baseball victories. Tsubasa, a girl who lacks self-confidence, wants to voice her opinion through her instrument of choice, trumpet, while Daisuke wants to join the school's baseball club and win the regional championship. The two make a promise that they will join the brass band and baseball clubs, respectively, and support each other for the championship.