Yuuko-chan 100 Renpatsu!!

Soon after transferring to a new school, Mayu Kodabutsu recieves a love letter from a cute girl named Yuuko Hai... Expecting the envy of his classmates, Mayu is surprised to recieve condolences instead. You see, Yuuko Hai is no ordinary 5th grader... She's an exorcist. And Mayu is destined to experience her 100 terrifying ways.

(Source: MangaWorld)