Kenshiro stands as a central figure across the narrative periods focused on Toki. In youth, he trained rigorously alongside his adoptive brothers Toki and Raoh under Ryuken in Hokuto Shinken. Observing Toki's practice, he explicitly acknowledged Toki's superior technical grace and accuracy compared to Raoh's reliance on brute force, demonstrating deep respect for Toki's abilities. Regarding Hokuto Shinken's succession, he firmly declared he would refuse the role if chosen, believing himself unworthy next to Toki, and intended to pass the succession directly to Toki, citing a historical precedent within their lineage. His bond with Yuria began early, the two often seen together during their youth at the Hokuto dojo.

When nuclear war erupted, he accompanied Toki and Yuria as missiles struck near them. Seeking safety, the trio reached a nearly full shelter. As the shelter door began sealing shut, Toki forcibly pushed him and Yuria inside to save them, sacrificing his own safety and exposing himself to lethal radiation. Trapped inside, Kenshiro reacted with immediate desperation, desperately trying to force the door open against Yuria's pleas to protect those already sheltered. This event caused Toki's terminal illness and fundamentally shaped Kenshiro's subsequent path.

Emerging after the nuclear holocaust, Kenshiro became a fighter navigating the post-apocalyptic wasteland. His connection to Toki remained significant, leading him later to join Toki, Bat, and Lin at a hilltop location historically important as the place where Toki and Raoh began their Hokuto Shinken training. He recognized the symbolic weight of this place as the destined stage for the impending confrontation between Toki and Raoh, fulfilling their childhood promise. His journey positioned him as a key inheritor of Hokuto Shinken's mission to bring peace in a violent era, a principle imparted by Ryuken.