Loretta Oratorio and Mirabelle Graceland are two thieves looking to steal an object of great power: The ARMS. They break into Alcatraz, the floating prison in the sky, and soon meet Dr. Kiel Aronnax, who escapes from imprisonment. The three try to escape, while trying to find the treasure, but instead stumble upon a mysterious ten-year-old boy named Sheyenne Rainstorm!