Kotarō Tojima is one of five high school boys recruited by Sakiko Horinomiya to compete in the "Motemen Koushien" tournament, aiming to win prize money for repaying debts owed to her. His defining trait is an excessively cute appearance that consistently undermines his perceived seriousness. This physical characteristic negatively impacts his social interactions and erodes his personal confidence, as others repeatedly fail to take him seriously due to his cute demeanor.

No specific familial or historical details define his background. Throughout the competition, Kotarō participates in group activities focused on refining social appeal and confronting interpersonal challenges. The tournament serves as a catalyst for collective personal growth among the boys, though Kotarō's individual developmental arc remains undocumented. Group interactions emphasize shared experiences in addressing their respective flaws, but his specific relationships or conflicts receive no elaboration.

No expanded backstory, alternate timeline depictions, or supplementary character development exists in OVAs, spin-offs, or other official extensions beyond the original narrative.