Katsuya Niimi, a former junior high track star holding national records in the 100-meter and 200-meter sprints, enters Seishū High School alongside his friend Susumu Karasawa. Witnessing the school's baseball team lose a game as Nakao Yuri, the coach's daughter and team manager, watches in tears motivates them to join the struggling team to make her smile.

Though initially lacking baseball experience, Katsuya's exceptional speed earns him the position of center fielder, wearing jersey number 8. His athleticism significantly boosts the team's dynamics as they fight to improve and avoid disbandment. His primary motivation, seeing Yuri happy, gradually evolves into romantic feelings for her.

His connection with Yuri becomes complicated when Yasuda Yukimi, a track athlete transferring to Seishū, actively pursues him due to a longstanding crush. Katsuya avoids directly rejecting Yukimi to spare her feelings, while also hesitating to confess to Yuri. This indecision strains team relationships, prompting teammate intervention. The conflict intensifies with the arrival of Jirō Yamanaka, a new team member and younger brother of rival pitcher Kentarō Yamanaka, who develops feelings for Yukimi.

Katsuya's rivalry with Kentarō Yamanaka extends beyond baseball; Kentarō is also Yuri's childhood friend and romantic competitor, pressuring Katsuya to clarify his intentions. His emotional avoidance fosters misunderstandings, leading Yukimi to misinterpret his reluctance as potential reciprocation. Key events eventually force Katsuya to confront his feelings more directly, resulting in candid conversations with Yukimi about his commitment to Yuri.

His journey involves recognizing the value of teamwork beyond individual goals, evolving from a solo athlete to understanding his essential role as one of nine players dedicated to the team's collective success.