recapped movie student manipulates 2 teachers in to sleeping with him

Hyo-joo (Ha-neul Kim) is a temporary teacher at a boys' high school and Hae-yeong (In-yeong Yu) is a fellow teacher who is the school board chairman's daughter. One day, Hyo-joo witnesses Hae-young locked in a passionate embrace with a boy and she starts feeling an inexplicable sense of humiliation towards Hae-yeong.