Heizo Onikawa, alias Onihei, is an elderly wrestling master famed as "The Destroyer" for his bone-shattering techniques. Despite his brittle frame, sparse white hair, and missing front teeth, he lacks visible muscle yet dominates opponents with ruthless efficiency. Initially enforcing wrestling hierarchy through brutality—like breaking Kouji Funada's arm without remorse—his loyalty to Iron Kiba meant absolute obedience. His persona shifted after a pivotal bout with Kiichi Miyazawa, where restraint and respect revealed a hidden kindness beneath his destructive reputation. Post-retirement, he renounces violence entirely, embracing hobbies like model airplane assembly and declaring a preference for creation over destruction.

Onikawa trained in locks and competed professionally, but his lightning-fast, technically intricate grappling style failed to captivate audiences, hastening his exit from the ring. He spent three decades as wrestling’s unseen enforcer, maintaining order behind the scenes while mentoring Kiyomasa Samon—later known as "the devil." He married and fathered a daughter, Aya. Samon’s betrayal left Onikawa hospitalized with a shattered arm, yet even wounded, he warned Kiichi of Samon’s monstrous power, prioritizing others’ safety over his own anguish.

His combat legacy rests on blindingly quick submissions that bypassed defenses to end fights instantly—efficient but unspectacular, sustaining his enforcer career for 30 years. In retirement, he fully abandoned "The Destroyer" identity, focusing on family and craftsmanship. His influence endures through Samon’s rise and his shadow stewardship of wrestling, though his twilight years cherish peace over conflict.