Moon Dong Eun had to drop out of school because of school violence. Since then, she has lived with thoughts of revenge. Years later, her main abuser got married and gave birth to a child. The former victim becomes this child's homeroom teacher when he goes to elementary school. So begins her long and difficult path of revenge. It targets not only the main offender, but also all those who watched the violence, but did nothing. Joo Ye Jung is a carefree and smiling guy. Instead of being the fairy prince Dong Eun, he decides to become the means of her revenge.