Dr. Izumi, sometimes called Professor Hurigen, heads the Daimobic research and defense base after its founder, Dr. Isamu Ryūzaki, is assassinated during failed Earth-Baam peace talks. He assumes leadership and oversees operations of the super robot Daimos.

As Kazuya Ryūzaki's maternal grandfather, he raises Kazuya following the death of Kazuya's mother and his father's departure into space. He personally trains Kazuya in karate to black belt level, essential for piloting Daimos due to its motion-synchronization system and providing a combat advantage.

Scientifically, he upgrades Daimos's energy systems using Daimolite particles and develops new weapons to counter Baam threats through collaboration with Dr. Douglas Banks. His leadership includes coordinating defense strategies and supporting field operations involving the support jet Galva FX-II and its pilots.

Politically, he opposes General Miwa's xenophobic policies and warmongering. He intervenes when Miwa illegally imprisons Kazuya, attending United Nations proceedings to secure Kazuya's release and expose Miwa's misconduct, reflecting his advocacy for peaceful coexistence with the Baam.

He survives severe injuries from a Daimobic base attack, recovering to continue leading Earth's defenses. His resilience is tested again when Daimobic relocates to a former Baam underwater base, where he helps thwart Miwa's attempted takeover.

Throughout the conflict, he maintains Daimobic as a familial environment, overseeing operations alongside his granddaughter Nana Izumi and providing stability for the crew, focused on protecting Earth while seeking diplomatic resolutions.