TV-Series
Description
Professor Gennosuke Yumi succeeded Juzo Kabuto as director of the Photon Power Laboratory. A middle-aged man with dark hair, a mustache, and glasses, he typically wears a white lab coat over a yellow shirt and black tie.

Having studied robotics under Juzo Kabuto, Yumi assumed leadership of the laboratory after Juzo's death, becoming the primary advisor to Mazinger pilots like Koji Kabuto. He possesses significant scientific expertise, constructing the Aphrodite A robot from Juzo's notes and transforming the laboratory into the hidden defensive Photon Power Fortress.

During conflicts against Dr. Hell and Baron Ashura, Yumi coordinates defense strategies, analyzes enemy Mechanical Beasts for weaknesses, and manages operations during attacks. He prioritizes preventing Photon Energy and Super Alloy Z from falling into enemy hands, once attempting to self-destruct the laboratory to achieve this. Viscount Pygman tricked him into lowering the laboratory's barrier, triggering the self-destruct. Both survived the explosion, and Pygman attempted to kill Yumi before intervention by his daughter Sayaka piloting the Venus A.

His operational decisions include advising tactical retreats, activating energy barriers, and evacuating personnel during crises like attacks by Ghost Mechanical Beasts. In the final battle against Dr. Hell, he revealed and unleashed the Photon Power Fortress’s cannon to destroy Count Brocken. He witnessed the resurgence against the Hell King Gordon through Gamia Q3’s energy polarity reversal and the Mazinger Army's combined efforts.

Yumi is mild-mannered and composed, dedicated to the laboratory’s mission even when pilots act recklessly. He shows deep concern for his daughter Sayaka and extends support to Juzo’s grandchildren, Koji and Shiro Kabuto. His name is occasionally rendered as Yanosuke Yumi in certain media, though Gennosuke remains the primary iteration.