Kenyuu, a 17-year-old monk at Zenou Temple, trained under Godai Sanzo. His exceptional intellect and mastery of sutras, honed through an advanced PhD program, were undeniable. However, his rebellious nature and dismissive outlook, perceiving most challenges as unworthy of his abilities, cost him consideration as Godai Sanzo's successor. Kenyuu believed existence required life-or-death stakes for meaning, embodied in his "Eat or Be Eaten" philosophy.

When Godai Sanzo formally announced successors without including him, Kenyuu violently confronted his master demanding answers. He then shattered his confinement and attacked the selection ceremony, defeating all potential successors before killing Godai Sanzo in rage. This violent act fulfilled the succession requirement by force, making Kenyuu the new Sanzo priest, though the gods never granted him the symbolic red chakra forehead mark signifying their blessing. Koumyou Sanzo witnessed the aftermath, perceiving hidden grief beneath Kenyuu's bloodstained exterior. Koumyou took responsibility for the new priest, bestowing the name Ukoku Sanzo. They traveled together for approximately one year.

Now Ukoku Sanzo, he retained ties to Koumyou, periodically visiting him at Kinzan Temple. During one visit, a significant conversation about Ukoku's enduring "Eat or Be Eaten" worldview led to an agreement known as "The Bet." The exact terms and stakes remain undisclosed, though it involved the symbolic "next rising sun" and profoundly shaped Ukoku's path. Years later, during a demon attack on Kinzan Temple, Koumyou used a binding spell to immobilize his young disciple, Genjo Sanzo (Kouryuu), sacrificing himself to ensure the boy's survival. Ukoku Sanzo's presence lingers around the events of this attack.