In the turbulent late Joseon period, the sons of former direct advisors to the Daewongun swear an oath of brotherhood before Magistrate Choi Nam-hyun, vowing to resist the tyranny and oppression of Queen Min. Under the guidance of the leader of the Hwalmin school, they hone their martial arts, waiting for an opportunity to save the nation. There, they encounter a beautiful woman disguised as a man who, like them, is training under the master to avenge her father. Despite facing numerous hardships, they ultimately succeed in their quest for vengeance.