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？

Having made his decision, Baiyi saw no other reason to stay at the party, so he returned to the Warrior Walker, who had long since stolen the show with her transformations. The pair left immediately after.

With this mission pending, the other formal obligations Baiyi had — including his position as a panelist to review theses — were instantly set aside. The secretary proved himself to be a capable individual, drafting an official letter from the Empire's military to the Sorcerer's Association. The letter would reach its intended recipient first thing in the morning.

Baiyi could not help but grin because of this. This young secretary displayed a high level of quality that only Da Xue's students could achieve. It was, however, still a surprise that the young man had only graduated from an Advanced Class. [1]

Hello, Pillow. Meet, Sleep