The plot follows Ok-ju, a highly skilled former bodyguard who is emotionally detached from the world until she reunites with an old friend, Min-hee, a ballerina. Their friendship is brief but profound, cut short when Min-hee takes her own life. Before her death, Min-hee leaves a plea for Ok-ju to seek revenge against a man known as Pro Choi, a sadistic criminal who filmed and blackmailed her. This sets Ok-ju on a relentless path of destruction, where she uses her lethal combat skills to dismantle a trafficking ring and confront the man responsible for her friend's suffering.