The Post-Apocalyptic Roadmap/Japan
The Post-Apocalyptic Roadmap/Japan
As the three years of war wore on, the Japanese quickly discovered they were abandoned by their American protectors who felt that the true war front was more important than maintaining their foothold in Southeast Asia. As American military forces were redirected to Alaska, their bases in Okinawa were left poorly understaffed-- ripe circumstances for a unified, Communist Korea and China to make a joint attack on the archipelago.
Nuclear devastation and the havoc it wreaked on the environment caused a surge in water levels, which caused many minor islands belonging to Japan to disappear, and forever change the shape of Japan's natural borders as the world knew it.
The conquered Japanese, sorely unprepared for any military action due to prohibitions placed at the close of WWII, became second-class citizens in their own country, as they were removed from all levels of upper government, as well as became a source of manpower for their high-casualty armies.
The population of Japan died off in vast numbers, as their land became irradiated, and their two conquerors blockaded any relief efforts to import food for the starving populace. It's not surprising to note that, due to their feelings of abandonment by the Americans and the harsh treatment they received from the Koreans and Chinese, the Japanese became extremely xenophobic-- both in heart and in local government legislature (except towards their new masters anyway). As a result, most prefectures enact isolationist practices that put even the Japanese Meiji-era paranoia and elitism to shame.
Without any sizable resources coming into or out of Japan, the economy is in ruins. Theirs is a nation built on loosely-tied prefecture-states, as their captors manage the country only in name (yet severely punish the slightest offenses, as though righting their common cultural hatred of the Japanese, who once conquered and committed atrocities in both Korea and China).