Tateaki Kiryuu, Nagumo Tatsuo's cousin and an anime-exclusive character absent from the original manga, begins as an ordinary human thrust into supernatural conspiracies when targeted by Faust Münchhausen II. The antagonist plots to resurrect the ancient entity Kyō-Ō using Tateaki as a sacrificial vessel, engineering a plane crash to achieve this goal. Severely injured in the crash, Tateaki survives only through an emergency blood transfusion from Nagumo. This transfusion introduces Chōjin (Overfiend) blood, triggering irreversible physical and psychological metamorphosis. The Chōjin blood catalyzes Tateaki's transformation into Kyō-Ō's host, mutating him into a monstrous form with bulging muscles, horns, and complete loss of human autonomy. Under Münchhausen's psychological manipulation and Kyō-Ō's corrupting influence, Tateaki commits sexual violence and murder. His mental state fractures as he battles internal corruption, embodying toxic masculinity and identity erosion. Münchhausen exploits Tateaki's residual humanity, perverting his emotions toward loved ones into violent impulses. A tragic romance with beast-woman Megumi Amano becomes central to Tateaki's arc. Despite Megumi's genuine affection, his corruption strains their bond. She emerges as a pivotal figure in his struggle between fading humanity and Kyō-Ō's malevolence, symbolizing potential redemption. Tateaki's narrative culminates in a skyscraper confrontation orchestrated by Münchhausen in Shinjuku. During the battle, Megumi deals Tateaki a fatal wound to halt Kyō-Ō's full awakening. His death terminates his role as a corrupted pawn, neutralizing the immediate threat while highlighting themes of manipulation and inescapable tragedy. His arc explores innocence corrupted, morality's fragility under external forces, and destructive consequences of supernaturally inherited power. This story remains confined to *Urotsukidōji II: Legend of the Demon Womb*, with no expansions or appearances in subsequent films, seasons, or spin-offs.