Since this EX volume is gonna finish up the Wilhelm backstory arc, and i'm surprised that this volume is one of the shortest one in history in LN, and if it would get another volume, I wonder, whos backstory we chould see next. The only characters I can think of is:
Al: We would like to see him how he got transported to the other world and would like to see his 20+ years in he's stuck in the other world and how he first met Priscilla.
Ricardo: OMG! WE WANT TO SEE HIS 40+ YEARS OF RICARDO'S PAST, HIS RACE, HIS TRIBE, AND/OR THE FOUNDER OF FOI. WE WANNA SEE IT AFSAFP!
Otto: TBH, as much I don't like him, it kinda grew on me and accept him as a character. It kinda intrest me to see his life of how he got his Divine Protection and 1st met Verhoe(or his other name in the WN, IDK).
Echidna and the whiches of sin: It's.....kinda intresting to see the life of the 7 whiches before they got killed my Satella. And what's funny is that i would like to see how they were killed by Satella. XD
...and.....that's pretty much it. lol Based on the chapter and arc where i am, i guess that's only i can think of. (Note: This post was intentionally going to be in the EX3 comment, but the comments was locked out for some odd reason.)