Rei, a high school girl, once lived in hiding with her father, who was involved in illegal gun trafficking. However, her father was murdered by two men: one with a red gun and another with a cross tattoo. As she grew older, Rei started dealing in guns, guided by Lin, who taught her about firearms. One day, Lin informs Rei that he has found the man with the cross tattoo, leading her to pursue her father's killer for revenge.