SLIGHT SPOILERS
Mainly just a critic of the writing.
This story stays pretty consistently good throughout but it's hard to take it seriously when every character has 12 dues ex machinas up their sleeve. I'm at chapter 60 I don't think there has been any training/grinding at all, it's all just power ups. The scaling is abysmal and doesn't mean anything, apprentice knight side characters are able to easily take down SS rank monsters with single strikes. I get not wanting to dwell on every little fight but why make it a point to show how overwhelmingly powerful their enemies are when they're just going to easily beat them anyways.
Ex is a boring main character, he hasn't earned anything. His power isn't being the hero of thief it's ludicrous amounts of plot armor, which kinda defeats the purpose of his type of character in my opinion. His nature as a cocky underdog is undermined when he doesn't do anything with his own power, it just turns him into a Gary Stu who's also kinda a dick. His power contradicts the limits it gave itself every other chapter. Something like, "You can't steal multiple skills from one enemy", he then proceeds to steal multiple skills from one enemy before he even got a power up or anything that would negate that limit. Again, why even put these scales and limits on things if they don't mean anything.
Hardcore Leveling Warrior also has a scaling issue but it's more justified in that story because at least they're using their own abilities and skills to get to the point that they're at (even if there is some BS thrown in here and there).
I get this is just meant to be some eyecandy prequel but it always irks me when there's something good that's tarnished for no discernable reason. Yee, vent over.