In the near future, humans abandon a devastated Earth and travel to outer space. However, due to an unknown phenomenon that prevents them from traveling into space, humanity returns to Earth only to find it inhospitable except for Eurasia. To accommodate the entire human population, pocket dimensions are created around Eurasia to house the populace. In order to find a way to return to outer space, the humans begin reenacting human history according to the Holy Book Testament. But in the year 1413 of the Testament Era, the nations of the pocket dimensions invade and conquer World, dividing the territory into feudal fiefdoms and forcing the original inhabitants of Japan to leave. It is now the year 1648 of the Testament Era, the refugees now live in the city ship Musashi, where it constantly