Jae-ha will be a vampire hunter recently arriving to town, attracted by the vampire attacks/rumours and the general mayhem, yes. But when he was a child, he was actually supposed to be offered by his village to become one of Yona's E. He refused and escaped, of course, and he holds Strong Feelings (tm) against the vampire/prey thing. He's going to meet Yona during the event, not knowing she was the pureblood he was supposed to feed.
Now, like a plus, I noticed there are a couple of charas who have a similar FREE THE PREYS thing, and I was thinking some of them could form a boyband group of hunters united by this same vision/feeling about the whole preys ordeal? Like, they travel together from town to town and hunt vampires to free their preys, and now are arriving to vampireau!town. I'm making a parallel here with Jae-ha being part of a pirate crew, so it would work for him to be part of a hunter band, but if anyone else is interested in the idea, I'm all up to plotting something about it!