Cap is a middle school student recognizable by his ever-present baseball cap. He serves on the Student Council alongside Hoshi and Pony and shares a pre-existing friendship with Nagara from their youth baseball team days.

After being transported to an alternate dimension through Hoshi's manipulation, Cap is thrust into a leadership role among the students. Despite his imposing physical size, he possesses a naturally kind-hearted, timid, and emotionally immature disposition, leading to intense self-consciousness and susceptibility to outside influence.

His ability, "All-Purpose Room," generates objects by concentrating in empty spaces, fulfilling the group's practical needs.

During his leadership tenure—empowered by the role and the dimension's rule preventing permanent harm—Cap adopts an authoritarian demeanor, fixating on order enforcement. This culminates in a violent outburst where he attempts to bash Asakaze's head with a baseball bat, relying on the world's rules to negate consequences. The act underscores his volatility under power dynamics.

Removed from leadership, Cap reverts to his inherent gentle and simple personality. He exhibits overt guilt and remorse for his actions as leader, particularly the assault on Asakaze. His arc illustrates the conflict between his enforced authority and his true, passive nature.