This is the story of a young girl named Ok Chang Mi, who dedicates her life to finding her twin brother's killer and carrying out a plan of revenge. Nineteen-year-old Ok Chang Mi used to be a member of the school shooting club and is skilled with weapons. Her brother died under mysterious circumstances exactly at midnight. In her quest to uncover the truth, the main character starts communicating with Ji Su Hon, the main defender of all the humiliated and insulted at school.