On the 15th of October 1990, World War III breaks out. It only lasts for 40 minutes, but industrial establishments were nearly wiped out by the 1000 megatons of nuclear weapons used in the war. The Earth was then cloaked by in a nuclear winter which lasted for 6 months, and all the grain plants died. Each government fell into anarchy and transport and communication networks could not be restored easily. Soon, declarations of state establishment from the citizens in various areas came one after another, and America was split into 6 parts, adding other unapproved small states, it was divided into more than 20 countries. The story is set in 2021, 31 years after World War III. Filicia Epstein, a bionics genius, came to Sabano and Sergent Mutou was ordered to protect her. Searching for her only brother, Lyon, Filicia encountered with 1019, a cybernoid, who directed them to the phantom city, OZ, which is a shelter created by Lyon. As the story unfolds, they gradually realised what 'OZ' actually was...