Hey that's actually pretty cool, so he could change his gender to fit the person and then lure them to give him sexual energy. I know he's a succubus and all but I haven't seen much manga or manhwa that shows this aspect. (Usually it's just incubus = boy succubus = girl, not that the creature could transform to either one which is a shame because that's one theory of the myth that I like explored.)
Definitely hooked, I'm looking forward to more!