Matias

Matias is a recruitable character that can be found in the Loser City Librarby.

You must collect books 5 to 8, then pass his little quiz in order to recruit him.

His quirk in battle is studying. If Matias lose one turn studying, he will unlock 4 magic spells (unless the mages already teached him) and increase his damage by 1.5x times.

The game itself describes him as:

"Small grumpy douchebag. Acts like a asshole, but cares about his friends."