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？

Generally, once a cape was taken off, a transformation sequence would occur.

Streams of Void Energy surged into Baiyi's body without a moment's rest. The change in his mien was so abrupt, the assassination team felt it, too. However, most of them could not feel the sudden increase in oppressive force as much as the Northern Warrior did, and it made his face go pale instantly.

He suddenly felt like a moth eagerly rushing towards a blazing flame. That realization made the Northern Warrior change his direction, despite having just mustered up some power himself. He slowed down to a halt and leaped backward as quickly as possible, instead.

Suddenly, Baiyi froze. The Void Energy, which had just surged into his body, suddenly changed into average mana, and the mana surged out of his body intensely. All that build-up towards his comeback move: Specialized Encasement Shaping Spell... had turned into average mana?

A Sinister Hunch