Professor Gennosuke Yumi directs the Photon Power Laboratory, succeeding his late mentor Dr. Juzo Kabuto. He directs the laboratory's operations and scientific research, including robotic technology development. His creations include the Aphrodite A robot, designed for peaceful applications and initially lacking offensive weaponry despite repeated requests from its pilot, his daughter Sayaka Yumi. This design reflects his commitment to non-military uses of photonic energy and advanced alloys, honoring Dr. Kabuto's vision.

During conflicts involving Mechanical Beasts or demonic threats, he advises pilots defending the laboratory and provides technical support. His responsibilities involve coordinating defense systems, analyzing enemy capabilities, and authorizing experimental equipment deployment, such as the Jet Scrander flight unit for Mazinger Z. He prepares for emergencies by memorizing critical technical blueprints and maintaining spare components for rapid repairs.

His professional oversight of Sayaka Yumi during missions is complicated by a dedication to scientific work that often leads to neglecting her personal needs and emotional well-being. He initially restricted her combat role and resisted modifications to Aphrodite A, prioritizing his perception of safety over her operational requests. He acts as a guardian figure for Koji and Shiro Kabuto, showing tolerance for Shiro's activities while frequently clashing with Koji's impulsive decisions.

When facing existential threats to the laboratory, including hostage situations or demands for surrender, he refuses to comply even under duress. He has prepared self-destructive countermeasures as a last resort to prevent the facility's technology from being captured. His scientific expertise encompasses Super Alloy Z and photonic energy applications, enabling contributions to mechanical improvements for defensive systems. He collaborates with laboratory staff on research projects while maintaining operational authority during crises.