Ja-Dou

Set in a mythological time and place, Ja-Dou recounts the struggles of the heirs to kingdoms of heaven and their comrades, to repel the demonic forces that sometimes make their way into heaven.
Ashray is the son of the Flame Emperor, small for his age, and cursed with a fiery temper. He also has to hide the fact that he has a horn, a trait usually associated with demons. His father keeps appointing assistants to keep an eye on him, but keeping up with Ashray is hard work, and the first six have died in the line of duty. Can Alan Seoul, his newly appointed seventh assistant, last a little longer than the first six? Teiou is a prince of the eastern kingdom of air. His best friend and lover is Keika, a mazoku, or demon, in human form. Tiarandear, is the Prince of the western kingdom of water. As chief of all the gods it is his job to maintain harmony in heaven and to direct and control human history. He loves Ashray, but how long can he keep protecting Ashray from the consequences of his violent temper? And if it should become known across heaven that Ashray might be part demon?
(For some reason, halfway into the 2nd volume there still is no mention of the northern prince.)