@ArcTicKronos I think that his skill makes the girls fall in love with him in higher levels. I think there was a chapter where he discussed that he will use the skill to conquer the girls, but use the skill at a low enough level to make them not fall in love.
I think the actual reason of why he's assignee there is because he's too powerful, and that wouldn't be good for the demon king or some other higher ups.