Do only Dark Knights acquire vices?


It seems that I only ever hear Ranta talking about getting the vice from a
monster's kill. I understand that by getting these he is able to level up
special skills related to his demon. Are Dark Knights the only class able to
acquire vices?




Short answer: **yes.**

Slightly longer answer.

In the beginning of the Anime, when the group including Ranta go to get their
class specific training, We are greeted with Ranta having a new ability with
him. The 'Vice' you mention. This is because, as we know 'Dark' knights, offer
up sacrifices to some form of a 'Dark lord' and have formed a pact. Just like
the Protag (I forget his name) got the ability to see an enemies critical
location, and follow a 'stream' of light with his blade, to reach it. Ranta
got his own class specific ability.

