Amon Ogata is a master swordsmith who serves as the adoptive father and teacher of Gai Ogata and the biological father of Sayaka Ogata. He discovered the infant Gai abandoned in the woods near his home; the child’s biological mother, Wakaba, had taken her own life while fleeing a killing rampage caused by her possession of the cursed sword Shiryu. Amon adopted the boy, raising him alongside Sayaka and eventually taking him on as an apprentice in sword making. Amon organized the Shiryu Cleansing ritual intended to subdue the sword’s power. The ritual went disastrously wrong when a participant named Tatsumi broke protocol, causing Sayaka to become possessed and attack Tatsumi. Gai intervened to save him but lost his right arm below the elbow. In response, Amon forged the cursed sword Shiryu into a functional prosthetic limb to replace Gai’s missing arm, attaching it up to the shoulder. This act integrated the demonic weapon into Gai’s body and enabled the young man’s ability to fuse with the sword in combat. On the surface, Amon appears as a caring father figure, but behind his paternal demeanor lies a deep internal conflict and a desperate wish for Gai to fully unite with the cursed blade despite knowing the dangers. As a swordsmith, his abilities are exceptional, capable of forging legendary blades such as the Shiryu and, in the anime adaptation, a new sword named Mikazuki forged from celestial steel. In his final days, Amon becomes overwhelmed by rising combat energy and is transformed into a demonic weapon, losing his humanity. In his last moment of lucidity, he asks Gai to protect Sayaka before being struck down.