|Family and Relations||Juzo Kabuto (Grandfather),|
|Voice Actor||Ayumi Fujimura|
|First Appearance||Activation! Mazinger!|
Shiro was born as the second son of Kenzo Kabuto and his eloped wife Tsubasa Nishikiori. When Shiro was still an infant, he and Koji were raised by their grandfather Juzo Kabuto, after the incident on Bardos. Koji and Shiro were told that their parents were killed in an accident to prevent psychological shock. With Koji taking the role of the "mother hen", Shiro had a pretty carefree life.
AppearanceEditShiro is a preadolescent boy with black hair and black eyes. His usual clothing consists of a yellow short sleeve shirt, dark blue shorts, and white sneakers.
Shiro is a lively young boy with a mischievous side, liking to poke fun at people like Boss and Inspector Ankokuji. Shiro however became rather close with Ankokuji for all that he has done for his family and was saddened when Ankokuji went missing in action. Since Shiro did not put much thought into his family until his grandfather's death, Shiro thought Koji was his only family left. Because of this and the power of the Mazinger Z, Shiro has full faith in Koji and the battles he gets into. Shiro was utterly startled when he found out that Tsubasa is his mother and the fact she killed his father. Upon hearing the whole story, Shiro begins to accept Tsubasa as his mother. Shiro also has a tendency to flirt with attractive girls, getting an instant crush on Lorelai Heinrich and giving perverse looks to the Gamia Q and Lori & Loru.
At the start of the anime, Shiro was kidnapped by Boss to lure Koji into a fight. Koji appeared and easily defeated Boss and his gang, with Shiro making fun of Boss. The Kabuto brothers were then brought on board the Hover Pilder before the craft combined with the Mazinger Z. Shiro was amazed of the robot and thought that its attacks were amazing. Upon Juzo dying from his injuries, Shiro was upset and mourned before witnessing Koji go on a rampage. After his brother calmed down, they were imprisoned by Baron Ashura disguised as Inspector Ankokuji. Shiro escaped from his cell and was about to break Koji out until Ankokuji tried to catch him. Koji ripped off the disguise, and Shiro broke his brother out. Shiro was then brought under the protection of the real Ankokuji as the battle against Ashura and his Mechanical Beasts commenced.
After the battle, Koji and Shiro moved into the Kurogane House. For several events, Ankokuji had to protect Shiro from threats like the Gamia Q that attacked the Kurogane house. Shiro would often make fun of him by calling him a 'gangster detective'. Shiro got a crush on a girl named Lorelai who came to visit the Kurogane House. When she offered to take Koji to meet her father, Shiro accepted and went to Germany. Shiro was a little startled to see Schtroheim Heinrich, but was more frightened when the doctor revealed that Tsubasa is his mother and that she killed his father Kenzo. Dr. Heinrich's castle came under attack by Baron Ashura and his Iron Masks. As Dr. Heinrich is knocked off the Danube α1, he explains to Lorelai her true origin as its core component and how to integrate into it. Shiro protests but Lorelai integrates with the robot as the Mazinger Z arrives. Shiro is found by Ankokuji who gets him away from the area to reactivate Gamia Q3, while Shiro made fun of the inspector's attraction towards the gynoid. Shiro escapes before the room is surged with energy and makes it outside to see the Danube and Z fight, telling both to stop. This fell on deaf ears as the Danube is destroyed by Z.
The loss of Lorelai and revelation of Tsubasa made Shiro feel uneasy back at the Kurogane House. Upon hearing from Koji what really happened to their father on Bardos, Shiro begins to lighten up to Tsubasa as his mother. For the rest of the series, Shiro would observe from the sidelines, the battles Koji and the others were in. Shiro was overjoyed when the final battle against Dr. Hell was won in their side's victory but this joy turned to fear when the Mycenae Empire rose up from underground.