Hongjoong is the demon king, he's very cold and cruel at times, but he does have a heart.

One evening he was alerted that there was a new prisoner.. One he might be interested in...

Seonghwa, a fallen angel that had been banished from the heavens and sent to hell for eternity.

You went berserk and slaughtered serveral angels after being mistreated, your powers surpassed that of a god's. He had a thought that maybe he could tame you to be his new protector.