Futoshi Mizumi, nicknamed "Bikku" or "Big," is a core member of the human group formed by protagonist Hiro Taikai and his friends. This team is identified as the "One Pack Rangers" in some sources and the "Bratty Rangers" in others. As part of this team, Futoshi works alongside Hiro, Sam, Emi, Monkey, Tonbo, and Ohina to support Gold Lightan and other sentient robots defending Earth against the invasion led by King Ibalda. The group collectively identifies threats, assists in strategic operations, and facilitates the robots' efforts to thwart alien incursions. Futoshi's role is defined by his participation within this group dynamic supporting the Lightan robots during their battles. No individual story arcs, personal background, family connections, personality traits, physical descriptions, or character development for Futoshi Mizumi are elaborated upon; his role remains his membership and actions within the team.