Kōichi Kawahara, a first-year student at Seirin High, plays basketball wearing jersey number 15. Standing 175 cm tall and weighing 64 kg with blood type O, he possesses an average height and very short black hair. His birthday is May 18. Kawahara is typically seen in Seirin High's red, black, and white uniform. He demonstrates strong determination and support for his team, actively cheering from the bench during matches. Kawahara also exhibits a humorous side, like recounting a childhood story during team introductions. His personal motto is "Purely and honestly." He dislikes fashion and spends free time being nagged by his older sister; his family consists of his parents and this sister. His favorite food is oden, his hobby is jigsaw puzzles, and he specializes in comedic "oden reaction" acts. In relationships, he is drawn to clumsy girls and currently shows interest in the opposing player Eikichi Nebuya. Initially joining the Seirin basketball club with skepticism and low motivation during the first-years' match against the second-years, Kawahara later missed the pre-Winter Cup streetball tournament due to illness. During the Winter Cup, he primarily supported the team from the bench but made his official debut in the finals against Rakuzan High, substituting for Hiroshi Fukuda in the second quarter. His stated reason for starting basketball was to build physical strength, and his best move is the layup shot.