Assassins Pride

Already 13 years of age, noble Melida Angel has yet to manifest her mana, and attends an elite academy where she is mistreated for her lack thereof. In order to help her, Kufa Vampir is ordered by the Angel family to become Melida's tutor. While Kufa seems to be a mere mentor, an ulterior motive lurks behind his job—he is to assassinate her if he confirms that she does not possess mana. (Source: MyAnimeList)