Akura-Ou

Akura-Ou is a major fictional character and antagonist from the manga and anime series Kamisama Kiss (Kamisama Hajimemashita). He is an infamous, powerful demon king (oni) who lived hundreds of years ago alongside his former partner-in-crime, Tomoe. Centuries ago, Akura-Ou and Tomoe wreaked havoc across the human and spirit worlds together as feared companion yokai. His immortal body was trapped in a fiery mountain in the underworld (Yomi-no-Kuni), but his soul escaped into the body of a deceased human teenager named Kirihito Mori. While Tomoe eventually changed after falling in love with a human, Akura-Ou remained ruthless until he was captured by the gods of Izumo. (This was requested, totally not forced-)