What type of demon is Yomi?

Just asking, just in case anybody had any ideas of their own they would like to share, 或者 knows of any exclusive information not 给 in the 日本动漫 或者 manga.

It’s for a 粉丝 fiction I'm 写作 and he's a character, and since I like to be thorough with my characters this information would help me out a lot. I am currently unfamiliar with any fandom concerning him, if there is any, so I guess I'm asking about that as well. I guess the real 问题 here is, what type of demon would 你 like Yomi to be, 或者 can accept him as in a 粉丝 fiction?

(*Note, there will be romance, I think, but not with Yoko XD)