Fifteen years in the future, by high-level scientific power, a violent battle takes place between the dimension La'cryma, that protects humanity, and the dimension Shangri-La, that plans the annihilation of all space-time. The key to stopping Shangri-La's invasion is a mysterious object known as "The Dragon's Torque." A group known as the Dragon Calvary is being set through space and time to find it.

In the present, twelve-year-old Haruka and her friend Yuu are contemplating running away from home when they meet a member of the Dragon Calvary named Karasu (Crow). He believes that Haruka has the Dragon's Torque and claims to be Yuu from fifteen years in the future.