Takeaki Kiryū is the human cousin of Tatsuo Nagumo, host of the Chōjin. Initially an ordinary and innocent individual, his life shatters when he survives an airplane crash deliberately caused by the demon Kohōki under Faust Münchhausen II's command. Critically injured, Takeaki receives a life-saving blood transfusion from Nagumo. Unknowingly, this infuses him with the supernatural Chōjin blood, initiating his transformation into a vessel for the ancient Kyō-Ō—an entity predating the Chōjin by millennia. Münchhausen II, seeking vengeance for his father's execution by the Nazis after failing to summon the Kyō-Ō, targets Takeaki to resurrect the entity and destroy humanity. Through psychological manipulation and demonic influence, Münchhausen corrupts Takeaki's mind, warping his emotions and driving him to commit violent acts, including rape and murder against loved ones. This corruption accelerates Takeaki's physical and mental metamorphosis into the Kyō-Ō, marked by bulging muscles, toxic masculinity, and eroding self-control. During his descent, Takeaki forms a romantic bond with Megumi Amano, a beast-woman and sister of warrior Amano Jyaku. Their connection embodies a star-crossed tragedy, as Megumi's genuine affection clashes with her awareness of his corruption. Despite her attempts to reach his remaining humanity, Takeaki's transformation proves irreversible. Their conflict culminates in a battle atop Shinjuku skyscrapers, where Megumi, recognizing the imminent threat, kills him to prevent the Kyō-Ō's full awakening, ending his role as Münchhausen's pawn. Takeaki's final physical evolution manifests as a hulking, horned demonic form, symbolizing his complete loss of humanity. His journey from ordinary human to tragic antagonist underscores themes of loss, manipulation, and the destructive consequences of external forces exploiting personal vulnerabilities.