Appearance
The Conspiracies
The conspiracies
Part of the main character's self justifications is his mild belief in the conspiracy that the kings of the world secretly worship the demons.
This belief is intentionally kept underdeveloped as it is both false and untrue even to the main character. Meaning, he is not sure he himself actually believes it. He only trots out this conspiracy when it is convenient to his self justification.
This conspiracy is not the driving force behind his actions, but a moral cloak for it. Meaning he is not a delusional conspiracy theorist but a dishonest rationalizer. Don't get his personality twisted and flanderized please.
His actual immediate motivation is the anger over the ignominy of what happened to his grandfather and the poor treatment he experienced as part of his local country's nobility. This is fed by his grandfather's stories of Sica, stirring revanchist feelings of restoring the glory of the past. Thus his main motivation is really a simple entitlement, or to put it more nicely, ambition. But he likes to pretend it is something more noble.
Development
The conspiracy has origins in fact. There exist demon worshippers in society, people who believe that demons are actually noble gods who tried to remove evil from human society and are instead being attacked by the evil capitalistic human society of the Solfrey. This belief has both religious and secular implications.
There are known religions and groups out there with this belief that the has heard of.
Radicalization Process
The MC's first exposure to this conspiracy during the story is from First Girl's stories of her schooling, where these ideas are whispered.