Koi-san is an anthropomorphic fish character in an animated series, serving as an Assistant Director on the television station production team led by Crayfish Senior. He occupies a senior position relative to the protagonist within their workplace ensemble, functioning as an experienced colleague in the production environment. His responsibilities center on participating in television production tasks and collaborative workplace scenarios alongside fellow team members. Visually, Koi-san displays distinctive fish-like attributes aligned with the series' anthropomorphic design approach. His documented role remains consistently situated within the main series' workplace setting throughout its broadcast run.