Koutarou Matsudaira is the catcher for the Meisei baseball team, defined by his steadfast supporting presence and athletic role. He stands as Kazuya Uesugi's best friend, their close partnership forming a central element of the team dynamic. Matsudaira possesses a buzz cut hairstyle and an overweight build. His position behind the plate involves direct, on-field coordination with pitchers, particularly evident during games working alongside Kazuya. His story centers squarely on this unwavering support and his active participation in baseball, with no documented personal backstory or character development beyond this role and his friendship with Kazuya across official media. His documented presence remains focused exclusively on these aspects.