Two years ago, Shibuya was ravaged by a biological terrorist  attack using the deadly Ua virus. Maria Osawa was saved when her father  inoculated her against the virus, but is left with partial amnesia from  the shock. She works as a cameraman when she reunites with a girl named  Canaan in Shanghai, China. A gifted assassin with synesthesia, she is  under orders from an unknown organization for a yet unspecified mission