Horizon in the Middle of Nowhere

Horizon on the Middle of Nowhere (境界線上のホライゾン, Kyōkaisenjō no Horaizon, lit. Horizon on the Borderline) is a Japanese light novel series written by Minoru Kawakami and illustrated by Satoyasu. The series is set in the distant future when Japan has been conquered by other countries and divided up into feudal territories. In 2011, it was adapted into an anime television series by Sunrise.

Plot
In the far future, humans abandon the devastated Earth and move to the upper world "Tenjo". But Tenjo and the law of causation collapse by a war and humans returns to the Earth, which has turns into an inhabitable planet except for Shinshu area. Shinshu is too small to accommodate all the humans, so they duplicate the area and create "Juso Sekai". In order to rebuild Tenjo and the law of causation, the returned humans start reproduction of history from B.C. 10,000. When the reproduction completes until A.D. 1413, a war breaks out in Shinshu and Juso Sekai falls onto the original world. The humans living in Juso Sekai lose their land and invade the original world. People in Shinshu surrender and is divided by the invaders from Juso Sekai. They try to resume the history reproduction from A.D.1457, but the update of history terminates in A.D.1648. A rumor of apocalypse begins to spread around the world.