Kim Jongin a.k.a Kai is a rebel who goes to a private high school due to his parents' conditions, he hates it there. Except for the times he get to spend with his friends, yes, all eight of them. Song Ji-hyo has just recieved her teaching permit, and she made it her goal to be a teacher in a prestigious high school (her first choice in her middle school days, yet she got rejected). To show them what a waste that they didn't accept her before. One is a bad woman, the other is mysterious boy. What ending shall they have? Will a forbidden love bloom in this teacher-student relationship?