Again for the first time. Reverse world
The distant past. At that time, mankind launched five huge wars called "World War" in less than 100 years, killing itself. But the few survivors who survived such war.
Through hard work, they restored the basic knowledge needed to rebuild human civilization. Then history was rewritten.
They decided to call their new living base "rebirthworld". It means "the reborn world". Correspondingly, it began to remake and use the calendar of "reverse force". Moreover, around 079, the era before the use of "reverse force" was divided into "old age" and "Neo age, N-age", so as to determine its historical significance.
Rewritten later human history "N-age"
It has been nearly three centuries since mankind settled in the current negative world. A considerable part of the once ruined earth has been repaired, and mankind has lived on most continents ...
