Moon Dong Eun was born into a poor family. During her high school years, she was unfortunately chosen as the target of bullying by a small group in her class, which included Park Yeon Jin and Jeon Jae Joon. Park Yeon Jin treated Moon Dong Eun with extreme brutality, scalding her with a curling iron until she was covered in wounds. Desperate, Moon Dong Eun thought of suicide, but ultimately she gave up the idea of seeking death, dropped out of school, and went to work in a factory. The only reason she continued to live was to take revenge on those who had bullied her one day. Years flew by, and through her own efforts, Moon Dong Eun successfully entered the school where Park Jeon Jin's daughter was studying and became her homeroom teacher. From then on, Moon Dong Eun's revenge plan began to unfold. She was determined to take revenge on everyone who had trampled on her.