Higanbana no Saku Yoru ni

Marie is trapped in a horrible situation. She's being constantly tormented by her classmates and regularly raped by her teacher. With nowhere else to turn, she finds herself asking for supernatural help from one of the seven demons of the seven mysteries of her school. All she desires is the death of her cruel classmates and teacher. How far will Marie be willing to go in order to achieve the murders that would free her from her living hell?

Wikipedia