Horizon in the Middle of Nowhere

Set in a crazy future where Earth is a no-go zone, humanity decides to pack up and head out to space. But surprise! An inexplicable force booted them back to a lonely planet, with Japan as the only livable spot left. To cope with the surge of people, they create pocket dimensions around Japan. Fast forward to 1413, and things heat up as neighboring pocket dimensions invade, splitting Japan into warring fiefdoms and pushing residents away. Now it’s 1648, and the last of the Japanese are aboard the city ship Musashi. With whispers of an impending apocalypse, Toori Aoi, student council president, rallies his classmates to reclaim their homeland.