Amano begins as a typical Tokyo high school student, immersed in ordinary teenage life. His existence shatters when the ancient Makai demon Jyashi violently possesses him, forcibly merging Amano's human mind with the demon's essence. This traumatic union inflicts severe physical and mental agony. As Jyashi's power grows, Amano's personality is increasingly dominated by the demon's aggressive, lustful, and destructive nature. His body transforms irreversibly, manifesting claws, horns, and enhanced musculature. Amano gains Jyashi's formidable demonic abilities—immense strength, speed, durability, and destructive energy—at the cost of his humanity. Fragments of Amano's original consciousness sporadically surface, particularly triggered by Akemi, a classmate he once cared for. These moments reveal brief flashes of recognition, remorse, or resistance, showcasing the fierce internal battle within the possessed form. The conflict culminates during a violent confrontation. Faced with Akemi's peril, Amano's spirit rallies, temporarily seizing control to protect her and confront Jyashi internally. This desperate defiance proves futile. Jyashi overwhelms and consumes Amano's remaining consciousness entirely. The possession becomes absolute and permanent. Amano's identity is obliterated, leaving only the demon Jyashi inhabiting the transformed physical vessel, devoid of any trace of the human student.