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 answer was filled with confidence, something that was characteristic of him. "What is there to worry about? You're just trying to reclaim what is rightfully yours; what's there to even prepare? As for the others I attracted, well... what do you think this whole thing was? It's the most sacred event of all time — your official ascension as the next Emperor of the Rohlserlian Empire! We need a big audience! Unfortunately, they were all I could attract to your event, Son. Can't help you more than that, so please accept my apology."

'You... You actually wanted to make this whole thing so big a spectacle?! Where is your elderly wisdom of keeping things confidential? And also... I knew it! You kept saying that the time of the Rohlserlians was no more, but at every given chance, all you remember is that massive and glorious empire!' Baiyi complained internally.

A Simple Prep Before The Excursion