Choi Sooyoung is your average college student, trying to finish her college degree in time. Or is she? In reality, Choi Sooyoung is not your average college student. She is actually an assassin, a vigilante. Trained in the arts of stealth, disguise and fighting, together with her partner, a computer genius named Kwon Yuri, who is in charge of tracking down people,   they hunt down and punish criminals who have slipped though the government's own justice system.