Naojiro Abashiri serves as the second son of Daemon Abashiri and a core member of the criminal Abashiri family. Initially presented as a gangster bearing a prosthetic right leg, his character evolves to expose extensive cybernetic enhancements, featuring mechanical limbs that detach to deploy weaponry such as machine guns and missiles. His large, muscular physical design became a recurring template reused across numerous works by creator Go Nagai.

Possessing immense strength, Naojiro frequently acts as the family's primary physical enforcer. He survives a structural collapse during a bank heist marking the family's disbandment by revealing his robotic nature, proclaiming himself "immortal" before retaliating with integrated weaponry. His cybernetic body grants high durability, enabling survival through explosions that leave only his conscious, communicative head functional. Later manga chapters downplay his cybernetic traits, shifting his portrayal toward a conventional strongman role.

His involvement in family conflicts includes battles against the Namakubi clan, where he confronts the supernatural Danjuro Namakubi. During this encounter, Danjuro's hair tentacles dismantle his body, though his head is recovered intact. In the "Cutie Honey vs Abashiri Family" crossover, Naojiro participates in defending Shura City's headquarters, utilizing leg-mounted machine guns in combat. The live-action film adaptation retains his cyborg identity, depicting him as a supervillain opposing the Namakubi family's microchip-based control scheme.

Within the spin-off *Mazinger Angels Z*, Naojiro attends high school while retaining his delinquent demeanor and superhuman strength. He frequently clashes with peers, effortlessly defeating groups like "Boss and his gang" with single punches. His personality includes persistent romantic pursuits, particularly toward Sayaka Yumi, though these advances are consistently rebuffed, often resulting in physical retaliation. He also briefly pursues Miki Makimura, attracting hostility from Akira Fudo.

Naojiro maintains a familial bond despite the family's criminality. He participates in routine activities like shared meals despite his robotic nature and engages in comedic antics, such as disguising himself as furniture to spy on his sister. During the St. Paradise School arc, he and Daemon launch a rescue mission for Kikunosuke, leading to his temporary disassembly. His character design also inspired variants like Naoko Sukeban in the *Cutie Honey* manga—a minimally altered gender-swapped version.