In 2067, an unknown disease struck Japan and was countered by an experimental vaccine. In actuality, the disease was created by Daiwa and the "vaccine" was used as an excuse for Daiwa to begin testing experimental nanotechnology. Every Japanese citizen was converted into a form of synthetic life. But there were unforeseen side effects; the conversion was imperfect, resulting in the infected humans losing their free will and becoming just lifelike machines. Some of the nanotech went amok, creating the "Jags", giant whirling constructs of semisentient metal that prowl the wilderness. The Jags destroyed all of Japan, save Tokyo which is protected by an inedible wall of ceramic.

Nice one. Thanks.

Will check it out, thanks.