Whistle! is about a middle school boy named Shō Kazamatsuri. He transfers from Musashinomori School to Sakura Jōsui Junior High School for better hopes to make the soccer team, since he never got a game at his old school due to his small stature. Yūko Katori, his teacher, introduces him as a former star of the famed Musashinomori team, causing his classmates to be wrongly ecstatic. Right after that, one of the players, Tatsuya Mizuno, reveals that he was never a regular. In other words, since he never got the chance to play, Shō is a poor player. Shō struggles to improve his skill so he can make the team at his new school and to ignore the drastic disadvantage he has due to his height.