Natsu ga Owaru made: Natsu no Owari The Animation

It is the story of Yui, a schoolgirl who accepts sexual harassment from her perverted teacher to protect the dreams of her boyfriend, Kou. After Kou lost in a match, Yui was summoned by the perverted teacher and had to visit his apartment because of an agreement the two had made. Between humiliation, suffering and pleasure, Yui gradually became a mere lustful sex object.