Kenzo Kabuto is a central figure in the narrative of Great Mazinger, defined by his role as a brilliant scientist, a father, and a man who carries the heavy burden of secrets. He is the son of the legendary roboticist Juzo Kabuto and the father of Koji Kabuto and Shiro Kabuto. Initially believed to have perished in a laboratory accident along with his wife, Kenzo was secretly revived by his father as a cyborg. His body, now largely mechanical, became a source of deep personal insecurity and a primary motivation for his actions.

Rather than return to his family in this altered state, fearing the psychological shock it would cause his young sons, Kenzo chose to hide. He went into seclusion, allowing his own father, Juzo, to raise Koji and Shiro. During this period of isolation, Kenzo learned of the impending threat of the Mycenae Empire. Driven by a powerful sense of duty and a desire to protect humanity, he dedicated himself to preparing for this new war. Using his father's designs for Mazinger Z as a foundation, he created a more powerful successor, the Great Mazinger, along with a new, stronger alloy known as Super Alloy New Z.

To pilot his new machine, Kenzo adopted two orphans, Tetsuya Tsurugi and Jun Hono, from an orphanage. He raised them and subjected them to intense training, forging them into the pilots capable of controlling Great Mazinger and the supporting robot, Venus A. As the director of the Science Fortress Laboratory, he served as their stern but deeply caring commander and legal guardian, treating them as his own children.

Kenzo Kabuto's personality is a complex mix of paternal warmth, secretive isolation, and unwavering determination. He is a good-natured and family-oriented man who deeply values human life. His decision to remain hidden was an act of love, a painful sacrifice made to protect his biological sons from a difficult truth. This secrecy, however, is a defining flaw. He is described as a secretive individual who only reveals himself when absolutely necessary. His insecurities about his cyborg body are a significant reason for this attitude, although his fears ultimately prove unfounded when his children accept him.

Despite his stoic and often reserved demeanor, Kenzo shows great affection for his adopted family. He is shown to be susceptible to the requests of his youngest son, Shiro, even building a small robot named Robot Junior to please the boy. His relationship with Tetsuya is that of a stern father and a respected son, though it is complicated by Tetsuya’s occasional jealousy over Kenzo's bond with Koji. When Tetsuya loses his fighting spirit or is injured, Kenzo offers to pilot Great Mazinger himself, demonstrating his willingness to sacrifice his own well-being for his charges. In the Shin Mazinger continuity, his personality is drastically altered when a parasitic organism called a Kedora, implanted by Dr. Hell, brainwashes him into becoming a cold and obedient puppet until he is able to free himself.

Within the story, Kenzo serves as the strategic mastermind and mentor from behind the scenes. Initially appearing in disguise as a prophet foretelling the arrival of the Mycenae Empire, he finally reveals himself to rescue his injured son, Koji, and to unleash Great Mazinger. He acts as the primary advisor to Tetsuya and Jun, providing tactical support and developing new weapons from the Science Fortress Laboratory. His relationship with his biological sons evolves over time. His reunion with Koji is happy and without resentment, though this closeness causes friction with Tetsuya. His relationship with Shiro starts with uncertainty but grows into a close bond.

Kenzo's development culminates in a final, heroic act of self-sacrifice. In a desperate bid to save the unconscious Tetsuya from the Flying Fortress Demonika, Kenzo crashes the Science Fortress Laboratory into the enemy vessel. He suffers fatal injuries and dies in Koji's arms. His sacrifice gives the Mazinger team the chance to regroup and ultimately defeat their foes, solidifying his legacy as a hero who prioritized the protection of others above his own survival.

Kenzo Kabuto’s most notable ability is his genius-level intellect in robotics. He is a highly accomplished scientist, capable of not only creating Great Mazinger but also developing advanced weaponry and support mecha. As a keen observer, he offers valuable advice to his pilots during combat. Furthermore, his existence as a cyborg grants him enhanced durability and a mechanical body, though his most significant contributions are always scientific and strategic rather than physical.