Shiro Kabuto, younger brother to Koji Kabuto, is the second son of Kenzo Kabuto and Tsubasa Nishikiori. After an incident on Bardos in his infancy, Shiro and Koji grew up under the care of their grandfather, Juzo Kabuto. To shield them from psychological trauma, the brothers were told their parents perished in an accident. Koji adopted a protective "mother hen" role, allowing Shiro a relatively carefree upbringing. A lively preadolescent, Shiro displays a mischievous streak, often teasing characters like Boss and Inspector Ankokuji. Despite this, he forms a genuine bond with Ankokuji due to the inspector's efforts to protect the Kabuto family, expressing visible sadness when Ankokuji disappears. Initially viewing Koji as his only remaining family after Juzo's death, Shiro places unwavering faith in his brother and Mazinger Z. He exhibits a tendency to flirt with attractive girls, developing an instant crush on Lorelai Heinrich and showing perverse interest in figures like Gamia Q and Lori & Loru. His involvement starts when Boss kidnaps him to lure Koji into a fight. Witnessing Koji defeat Boss and combine with Mazinger Z via the Hover Pilder, Shiro marvels at the robot's attacks. Following Baron Ashura's fatal attack on Juzo, Shiro mourns his grandfather and sees Koji's ensuing rampage. Imprisoned by Ashura disguised as Ankokuji, Shiro escapes and tries to free Koji before the disguised inspector intervenes. After Koji exposes the deception, Shiro aids his brother's escape and later receives protection from the real Ankokuji during battles against Ashura and Mechanical Beasts. Shiro subsequently moves into the Kurogane House with Koji. Ankokuji repeatedly shields him from threats, including an assault by Gamia Q on the residence. Shiro maintains his habit of teasing Ankokuji, dubbing him a 'gangster detective'. His crush on Lorelai leads him to accept her invitation to Germany alongside Koji. There, Schtroheim Heinrich reveals Tsubasa is Shiro's mother and that she killed Kenzo Kabuto. This revelation startles Shiro, compounded by Lorelai's integration into the Danube α1 robot during an Ashura attack. Shiro protests unsuccessfully and is evacuated by Ankokuji, witnessing the Danube's destruction by Mazinger Z. The loss of Lorelai and discovery about Tsubasa leave Shiro uneasy upon returning to the Kurogane House. He begins to accept Tsubasa as his mother after Koji explains the full circumstances of Kenzo's death on Bardos. For the remainder of the conflicts, Shiro observes battles involving Koji and others from the sidelines. He experiences joy at Dr. Hell's defeat but feels fear upon the emergence of the Mycenae Empire. In Great Mazinger, Shiro remains in Japan after Koji's departure. His character gains depth encountering his father Kenzo, previously believed dead. Shiro gradually bonds with Kenzo, who dies shortly after their reconciliation. During this series, Shiro becomes the pilot of his own robot, Robot Junior. Within the Shin Mazinger continuity, Shiro is present when Kenzo Kabuto is revealed to have survived by amputating his Dr. Hell-corrupted hand, which contained a controlling Kedora. Kenzo discloses to Tsubasa that defeating Dr. Hell would provoke the Mycenae empire's arrival.