It began when the Kim Dynasty imploded in civil war in 2021. By 2022, the two severed Korean states reunited, with the conspicuous absence of North Korean men. The country’s female population exploded, but amongst outsiders, the government didn’t seem concerned. Neither did Japan, despite it’s own decreasing birth rates.

This was intentional however, because in secret as the war ended in Korea, the two recognized the infinite danger of modern war. Of nuclear war. The centuries old territory dispute ended with a line drawn across the East Sea and extending to north pole and back down to the south.

Everything east of this line was Japan’s new domain.

Everything west of this line was Korea’s new domain.

And by the time the two met again, and drew a matching line in the Western Hemisphere, there would be no more men.