Demon Diary (Diary of the Demon King) by Lee Yun Hee, Lee Ji Hyong, and drawn by Kara Lim (Mangafox.com) - Lee Chi-hyong (volume one), Lee Yun-hee (volume two through seven), and Kara ( the name of the duo team consisting of Kim Yoon-gyeong and Jeong Eun-sook) (Wiki) is, again, one of the first manga I collected. I loved everything about it ^^
:
A number of writers have worked with Kara on the production of Demon Diary.
The story for volume 1 was written by Lee Chi-hyong. Lee stopped
writing, because he had to prepare for the upcoming high school exams.
The stories for volumes 2 through 7 were written by Lee Yun-hee.
: As said on Wikipedia.com
This was the first Shounen Ai manga I ever read and I have to say I wasn't even aware of it at the time - I think I was 12 years old and naive. I can't say too much about the main story though, I'm scared I'll ruin it for readers who haven't picked this good read up yet.
Genres: Action, Adventure, Comedy, Drama, Fantasy, Shoujo, Shounen Ai
Summary:
Gods and demons wage a never ending battle with the mortal realm as their
battlefield. As with most longstanding feuds, the reasons are no longer
important--hatred is a way of life. But it is foretold that one would
arise who could restore harmony between gods and demons. Enter
Raenef...heir to a set of demon royalty, he is hardly courtly material.
The demon king assigns Eclipse to be his tutor, to mold Raenef into
proper demonic shape. The two begin a journey of discovery and are soon
joined by a human knight and a god-blessed priest.
Picture found on Google*