Humans evacuate a damaged Earth and journey to distant space in the long future. However, owing to an unexplained phenomena that prohibits them from flying into space, mankind returns to Earth, only to discover that it is uninhabitable, with the exception of Japan. Pocket dimensions are being developed around Japan to house the whole human population. Humans began reenacting human history according to the Holy Book Testament in order to find a means to return to outer space. However, in 1413 of the Testament Era, countries of the pocket dimensions attack and conquer Japan, partitioning the area into feudal fiefdoms and forcing the original population to flee.