It should be noted that near the very end of the manga, when Ken was at his most ridiculous, he pissed Yuria off by not answering Bat's heart and Lynn's feelings for him, leaving a love triangle between them unresolved.
What happened next is freaky. Koukuoh(Raoh's horse) senses death coming, but Ken thinks its just his time. Ken then sees Yuria's image in the sky,
and she is not happy. The both of them get hit so hard by lightning that Koukuoh actually dies and Ken gets his memory wiped. Later on, Bat finds Ken and when he figures out what happened,
it turns out that Yuria was angered enough by Ken's actions that she caused his memory loss. While she was dead. This fact is reinforced by Yuria
actually appearing to Bat the moment he realizes what happened.
So yeah. Yuria might have actually been some kind of monster in her own right, but the only thing keeping her in check may have been her sickness, and her kindness. Ken had to return from the dead to kick Kaioh's arse. Yuria kicked Ken's arse
while she was still dead.
HNK2 and the manga ends soon after this.