the other side of the world

The youngest archmage in history was ambushed by his enmies, seeing that he was going to die, he used a forbidden magic which would kill him to take down his enmies with him, that was the end of the history of a hero and also the start of another one
He reincarnated as a baby named Ren in the modern era, because of the lack of magic power, Ren was simply a kid with a high intellect

Thanks to the advanced machinery , humanity explored 20% of the world, the remaining 80% was unknown,, any attempt at exploring it was useless,

When Ren was at 13, Magical power came back, and the chaos era started again, Humanity had to face the other side of the world