Iron Kiba, born Seiji Kiba, is the illegitimate son of renowned wrestler Daidou Rikiyama. After his father's death, he endured severe physical abuse from his mother, obsessed with Daidou, culminating in her attempting a double suicide by strangling him. Kiba escaped, though his mother was later found dead. Sent to live with Daidou's widow, he suffered relentless torture, confined to a rat-infested shed. These experiences forged intense rage and an obsession with absolute power within him.

Kiba received combat training from Gousaka, a mentor who perpetuated the cycle of abuse. This culminated in Kiba violently attacking Gousaka with a bat, using him as a training dummy to master fighting techniques. His early wrestling career featured victories over elite fighters, including an Olympic judo gold medalist and a heavyweight boxing champion, establishing his reputation. However, a clandestine, brutal match against Seiko Miyazawa of the Nadashinkage-ryu martial arts school resulted in mutual severe injury: Seiko suffered a broken collarbone and retinal detachment, while Kiba lost his left eye. This defeat became a profound humiliation, igniting an obsessive vendetta against the Nadashinkage style.

As CEO and champion of World Pro Wrestling, Kiba publicly championed professional wrestling as the ultimate martial art. Privately, he orchestrated a campaign to destroy the Nadashinkage-ryu. He manipulated fighters like Kiyomasa Samon and Kouji Funada into confronting Seiko and his son, Kiichi Miyazawa, employing underhanded tactics such as breaking promises and exploiting ambitions. He demonstrated willingness to inflict violence indiscriminately, including against children, and exhibited patterns of domestic abuse across multiple marriages. He possessed a tall, massive build, slicked-back black hair, and an artificial right eye, often concealed by sunglasses, typically wearing sophisticated suits.

After retiring from professional wrestling following a disqualification loss, Kiba sought no-holds-barred matches to prove wrestling's superiority. He arranged a rematch with Seiko, postponed when Seiko sustained injuries saving a drunk pedestrian. Kiba instead fought Kiichi in a near-five-hour brutal contest. Despite severe injuries, including shattered legs, Kiba won via German suplex, driven by hatred and indomitable will. This victory unexpectedly brought him a measure of peace, shifting his focus toward personal redemption beyond destructive vengeance.

Kiba later entered a violent martial arts tournament to cement wrestling's dominance but suffered a catastrophic 52-second defeat to Edgard C. Garcia, resulting in near-total paralysis on his left side and torn ligaments in his right leg. Though he concealed the extent publicly, his physical decline was irreversible. Facing critical heart problems and a limited lifespan, he sought Seiko's help for rehabilitation. Seiko employed risky Nadashinkage-ryu techniques to restore Kiba's mobility, further shortening his life expectancy. In a final act of defiance, Kiba tested his regained strength by battling a Siberian tiger barehanded before challenging Garcia to a cage-fight rematch. Trained in Nadashinkage-ryu by Seiko, who served as his corner man, Kiba broke Garcia's streak of instant victories, fighting valiantly for nearly an hour. Ultimately defeated, he expended his remaining energy and succumbed to heart failure one month later.