On the day of her ex-boyfriend's wedding, Siyeon causes a scene, then ends up sobbing in a hotel bar—when a man who seems both familiar and unfamiliar approaches her. Though his suggestion that he already knows her raises suspicion, Siyeon, desperate for comfort, ends up spending the night with him. The real problem comes after. The mysterious younger man turns out to be Cha Hajun—Siyeon's former student and the newly appointed teacher at her school workplace! Relentlessly closing the distance between them, Hajun begins making bold, shameless demands without hesitation. “Sir, Let's do it again— with me.”