Sixteenth Basket of Mantaos

Imagine being forced to live, after death, as incorporeal bodies trapped in a vast space of nothingness for thousands of years, with nothing to do but exchanging past memories with other cohabitants (read: weirdos).  Everybody wanted out, but there was no way to leave the Void... 
Until one day, a young man was finally summoned, as a powerful but reluctant mentor, by a bubbly and motivated but completely naive young girl. Baiyi, finally out of the Void, was the only one who could save all of the other 32 souls from their prison and his summoner might just be The Key to their freedom.
However, Baiyi had to use the techniques and abilities the other souls had taught him throughout the years, and together with his own extensive knowledge of anime and game tropes from his shady and dangerous past as an otaku, to face the biggest challenge of them all: training the clumsy young girl he was forced to partner up with… into a competent sorcerer!

EndlessFantasy Translation 

Why Did You Summon Me？

The Archmage's words left Baiyi quiet; the soul armature had retreated into his subconscious, reexamining his countless simulations and models. Sometime later, Baiyi discovered something unexpected: despite the Laws and methods used to build a world, if Baiyi did not interfere, every world he built would end in the same way.

It did not matter how perfect the world was at its beginning. Nature could be bountiful and stable and harmless; the world could begin with the absence of natural disasters, plagues, and other kinds of diseases, and thousands of years later, the world would end up like the others. It would contain happiness and desolation and be surrounded by miracles and disasters; maladies of all kinds would somehow return, and the people would end up divided.

'Humans will always make the same mistakes,' Baiyi thought, smiling helplessly.

A Quandary, Indeed