Since childhood, Yomi Takeda and Tamaki Yamazaki have shared a deep love for baseball. They would play catch whenever they had the chance, and during those moments, Yomi realized she had a special ability to throw the ball in a way that seemed almost magical. The two girls made a promise to continue playing baseball even as they grew older, but soon after, they were separated. In the following years, Tamaki developed into a talented catcher, whereas Yomi, despite her natural pitching gift, struggled to advance in the sport.
Choosing to give up on her passion, Yomi begins her first year at Shin Koshigaya High School. She tries her best to stay away from anything related to baseball, but she soon encounters the twins Yoshino and Ibuki Kawaguchi, both of whom are passionate about the game. Furthermore, she unexpectedly runs into Tamaki, and just like in the old days, they decide to play catch—rekindling Yomi's desire to pitch.
Now reunited, Yomi and Tamaki aim to keep the promise they made as children. Together with Yoshino and Ibuki, they work to bring back their school's baseball team, which has been inactive. More players eventually join until their roster is full, and the newly formed girls' baseball team of Shin Koshigaya sets its sights on nothing less than winning the national championships.