(from wikipedia.ja):

The story consists of three parts.

The year is 2222, in Megalopolis Tokyo. Shima and Yuki, both members of the government agency G Bureau, work to protect the government's secret "plan" from sabotage by various countries and organizations.

Part 1 - The Kamiyoshi Plan:

A plan to build a large number of interstellar spacecraft and emigrate the entire Japanese population into space. In conjunction with this plan, secret agreements are made to cede the land to other countries after the Japanese escape.

Part 2 - The Yayoi Plan:

Japan discovers the ore cosmonite, which contains enormous energy, in outer space and begins to use it exclusively.

Part 3 - III Plan
The plan is to eliminate all conflicts by cutting the earth in half and having the opposing parties live in separate hemispheres, but eventually it is decided to separate humans and robots, and Shima and Yuki are about to part ways.