대치동에서 탄탄한 입지를 다진 등급 올리는 귀신, 국어강사 서혜진. 오늘도 아이들의 등급 사수를 위해 밤을 지새우는데.. 밤 12시의 대치동처럼 고요한 그녀의 일상에 불쑥 첫 제자 이준호가 침범한다. 대기업 사원증을 버리고 학원가에 인생을 걸어보겠다며.
Famous star instructor Seo Hye-jin works until midnight at the academy like any other day. As she stares at the Hall of Fame in the lobby, Jun-ho's name catches her eye. He is one of her proud boast as she did her best to teach him, and he made it into a prestigious university. At the same time, Jun-ho decides to resign from his company and make a new beginning as a rookie instructor.