He will personally kill every demon he sees. Whether they are good or evil, whether he likes them or not, makes no difference. Xuanyuan despises demons. Night or day, he is always on the front lines of the demon hunt, shutting away his heart and acting alone. He has only one goal: to exterminate demons. Xuanyuan is like a blazing pile of firewood, burning through his own life. But even the hottest fire must eventually go out. He waits and prepares for the day it does, determined to kill the King of a Hundred Demons with his own hands before then. Until the girl appeared and knocked on the door of his tightly sealed heart.
Good guy, it's a complete mess
Damn, the King of Hundred Demons is no longer killing you!
The book is pretty good, but it's terrible.