Kyōtarō Ōtaki is a genius scientist who lived before the events of the series. He designed Victor City, a technologically advanced settlement intended to protect and preserve humanity in the wake of a global cataclysm caused by a radioactive meteor. As the father of Daigo Ōtaki and Saori Ōtaki, his work and legacy form the central pillar of the story. His primary motivation was to safeguard the future of mankind, and to that end he created a sophisticated multi-stage super robot defense system known as Gordian. He encoded the Gordian system to his son Daigo's DNA, ensuring that only Daigo could operate it effectively; an attempt by Saori to pilot it left her severely injured. Kyōtarō died before the series begins, but his influence persists through his children: Daigo, who inherits the Gordian system and joins the Mechacon 18th regiment to defend Victor City, and Saori, who secretly managed the city for years in his stead. His key relationships are therefore defined by his posthumous role as Daigo and Saori's father and the creator of the city and robot. His personality is not directly depicted, but his actions reveal a far‑thinking, protective, and methodical scientist who planned for extreme contingencies. His notable abilities lie in advanced engineering and genetics, particularly in designing a city‑scale shelter and a robot system keyed to a specific user's biological signature. Throughout the series, Kyōtarō's legacy drives the conflict between the Madokter Army, which seeks to seize the secret technology of Victor City, and those who defend it. He undergoes no on‑screen development, but his children's growth is directly shaped by the responsibilities and burdens he left behind.