Dr. Mizuki created the Arbegas robots, Earth's final defense against the invading Gerinya Empire following centuries of peace. He designed the trio of robots to combine into a single mighty metal giant. Piloting these robots are his daughter, Hotaru Mizuki, alongside martial artist Daisaku Enjouji and the aloof Tetsuya Jin. The robots operated from a mountain base and wielded an energy sword.
Plans existed to adapt the Arbegas series internationally as "Gladiator Voltron" (designated Voltron II), featuring the three robots combining into Voltron. This adaptation was ultimately abandoned due to the strong popularity of Lion Voltron (Voltron III), the lukewarm reception of Vehicle Voltron (Voltron I), and Arbegas's lack of significant success in Japan.
Official media such as movies, OVAs, or spin-offs do not document additional background, development, or expanded role for Dr. Mizuki beyond his function as the robots' creator and his relationship to Hotaru.