Mark of the Succubus Volume 1 Manga

Maeve, a succubus-in-training, is sent to the human world by her mentor, Veril, to learn how to blend in and hone her skills of seduction. The rules of the Demon World are complicated, though, one of them, "Don't fall in love with your target," looks like it might be a little too easy for Maeve to break, especially after she meets Aiden.