Tousaku Arai is the narrative's primary antagonist and leader of the Sonen Group. He falsely claims to be the reincarnation of Buddha, attracting widespread attention and followers through public demonstrations of seemingly supernatural abilities, such as halting a falling object during an earthquake. These powers originate from demonic possession, granting him capabilities like mass hypnosis and illusion projection, rather than genuine enlightenment.

Arai preaches a philosophy centered on selfishness and Social Darwinism, advocating personal advancement at others' expense. This directly opposes the altruistic and loving principles championed by Taiyou Sorano, the true Buddha figure. As leader of Sonen, Arai initiates hostile actions against Sorano's group, TSI, targeting its members. His tactics include inducing Shunta Amanokawa's illness via demonic possession and later launching psychic attacks against the public.

His conflict escalates through large-scale manipulations, such as creating a collective UFO invasion hallucination during a summer festival and simulating a catastrophic tsunami threat across Japan. Both events aim to establish his dominance by offering salvation in exchange for absolute obedience. The climax occurs at a baseball stadium where Arai kidnaps Sayako Amanokawa, threatening to kill 50,000 attendees unless she publicly acknowledges him as Buddha. When she instead declares Sorano the true Buddha, Arai attempts to kill her by throwing her from a hovering platform.

Confronted by Sorano, Arai becomes fully possessed by a powerful demon, revealing the true source of his abilities. After Sorano exorcises and defeats the demon, Arai is freed from its influence. He expresses genuine remorse for his actions and receives Sorano's forgiveness. Following his defeat, Arai is imprisoned. The epilogue depicts him converted to TSI's teachings, praying in his jail cell and expressing gratitude for his enlightenment despite his incarceration.