In Kamisama Hajimemashita, Akura'ou is a powerful demon with an immortal body that has been living for at least 600 years. The manga doesn't say much about the circumstances of his birth, except that the gods wept when he was born.
Appearance: he is very tall, has long red hair. Looks human except the large horns on top of his head and pointed ears.
Character: He is pretty much the force of chaos, loves war and slaughter.
The origins of other demons in the manga are more-or-less clear: Tomoe is a kitsune, Kurama is a tengu, Mizuki is a white snake, and so on. But it's unclear just what kind of demon Akura-ou is.
What inspired the mangaka? Alternatively, what characters from other manga/anime resemble him?