Sakura Sakurakouji is a superb martial artist with a spirit of fairness that never wavers—regardless of the scenario. When she sees individuals dying in blue flames on a bus trip home, she contacts the cops to bring their killer to justice, only to discover that no proof exists. All her misgivings about what she witnessed evaporate the next day, when new transfer student Rei Oogami joins her class; he is the exact kid she witnessed execute cold-blooded murder. Rei is polite and kind, and he soon gains popularity, despite Sakura's charges. Soon after, she discovers his actual nature: a Code Breaker, or "one who does not exist." To Sakura's surprise, Rei, armed with unknown powers, wants to exact punishment.