Keisuke Umehara serves in Nishiura High School's cheering squad, rallying support for the baseball team. Initially hesitant to engage with the players, his perspective shifted after witnessing the club's heartfelt greeting. He shares a longstanding friendship with Yoshirō Hamada, forged during their shared classroom days; though Hamada’s repeated year placed them in different grades, their bond endures. Keisuke also connects with fellow squad member Riki Kajiyama.

Visually, Keisuke stands out with long brown hair and gray-blue eyes. He typically sports the Ouendan uniform, acquired from a basketball team friend whose senior had recently graduated.

For tournaments, Keisuke, Hamada, and Kajiyama adopt the cheering squad’s formal gakuran attire, complete with a left-arm armband. Their primary role involves energizing crowds during the baseball team’s competitive games.