Nod. "Where do they all live, if there are more places than just Fairyland and here?"
"The sex demons need sex energy to...well, not to live, exactly, but it's food to them. For them, sleeping with someone has about the same emotional meaning that...wait, food envassals you. Well, it has the emotional meaning that having someone make you a sandwich has for mortals. A really good sandwich, if it's really good sex."
"Oh. ...Are these common? Should I ask you to order me not to have sex with any sex demons?"
"Probably not, no. Is it ever going to be a really good idea to have sex with a sex demon?"
"Oh. Okay, if that's the best reason. Are they pretty easy to tell apart from other people?"
"Then I'm not sure the order would work very selectively unless you told me not to have sex at all, and then I'd have to find you or give someone else mastery over me to get it reversed, down the line when I'm feeling better."
"And at that point we're back to you can let me know if someone propositions you so I can tell them it's not okay. They're not going to mojo you off the street, anyway--in all the cases I've heard of it happening, the victim was lured into a position where no one else would notice the incubus or succubus being supernaturally sexy."