Rumors spread among high school baseball players in Kanagawa Prefecture about a mysterious figure known as the Baseball Club Slasher, who appears at night to challenge players to a three-pitch showdown and is rumored to throw astonishingly fast pitches without ever losing. Heita Kobori, the captain of Yokohama Soha High Schools baseball team, dismisses these rumors but is himself approached by the Slasher one night. Impressed by the strangers pitching skills, Kobori aims to recruit him to the team with the goal of reaching Koshien, Japans most prestigious high school baseball tournament.

The stranger is revealed to be Fusetsu Kiriyama, a student at Soha High who possesses great baseball skills but suffers from a debilitating condition. A former member of the baseball team who retired due to a severe case of the yips, Kiriyama can only throw three good pitches per day before his pitching becomes far weaker. After his retirement, he began his nocturnal challenges as the Baseball Club Slasher, limiting every confrontation to just three pitches. Following his recruitment, Kiriyama joins the team as a reliever who can only be used for a single batter at a time.

The team also includes Yōji Hirose, a member who aims to become a sports researcher, and is coached by Minako Agawa, a classic literature teacher. With only three weeks remaining until the final championship of their third year of high school, the team places its hopes on Kiriyamas limited but powerful pitches to help them secure a path to Koshien. The narrative follows this dramatic and time-sensitive quest where every one of Kiriyamas pitches carries immense weight, creating a tense atmosphere of a baseball drama that begins in the bottom of the ninth inning.