Kyoukai Senjou no Horizon

In the far future, humans abandon the devastated Earth and move to the upper world \"Tenjo\". But Tenjo and the law of causation collapse from a war and humans return to the Earth, which has turned into an uninhabitable planet, with the exception of the Divine State area. The Divine State is too small to accommodate all the humans, so they duplicate the area and create the \"Harmonic World\". In order to rebuild Tenjo and the law of causation, the returned humans start the reproduction of history from B.C. 10,000. When the reproduction up till A.D. 1413 is completed, a war breaks out in the Divine State, and the Harmonic World falls onto the original world. The humans living in Harmonic World lose their land and invade the original world. People in the Divine State surrender and are separated from the Harmonic World by the invaders. They try to resume the reproduction of history from A.D.1457, but the update of history is terminated in A.D.1648. A rumor of apocalypse begins to spread throughout the world.