Futoshi Mizuki, nicknamed "Big," stands as the fourth member of the Bratty Rangers, a team of sixth-grade students allied with the sentient robot Gold Lightan. His extraordinary physical strength peaks during intense anger, allowing him to bend metal prison bars or support collapsing structures like roofs. Mizuki's civilian roots trace to his parents, who operate a flower shop with no involvement in interdimensional conflicts. Early in development, prior to mecha integration, this character bore the name "Cowboy" and featured a taller, slimmer design. The word "BIG" emblazoned on his shirt persisted into his finalized younger, physically imposing form.