Sumo Do, Sumo Don’t

A university student who reluctantly joins the sumo club to secure missing graduation credits. He becomes the team’s driving force, balancing ambition with caution while enduring injuries that test his resolve. By the end, he declines a job offer and remains committed to leading the club.

A traditionalist sumo enthusiast and the club's initial core member. He is instrumental in recruiting Haruo and Tanaka and emphasizes classic techniques. His perseverance helps sustain the team through early defeats and setbacks.

Shuhei's younger brother who joins the team. He shares a familial drive to prove himself, faces a serious arm injury, and contributes to the team's comeback with grit and resilience.

An overweight recruit who persists despite his limitations. He gradually demonstrates his ability in matches, inspiring teammates and catching the attention of the sport's scouts.

A graduate student and sumo club manager who prompts Shuhei's involvement. She plays a supportive, organizing role and develops a crush on Haruo, adding a personal layer to the team's dynamics.

A British student and seasoned footballer who joins to help save on rent and brings a fresh outside perspective to the club. He participates in training and leaves for Britain after the summer training camp.

The supervisor who offers Shuhei a deal: join the sumo club in exchange for overlooking missing credits. He acts as a mentor figure whose pragmatic approach drives the central conflict and arrangement.