"Your Majesty, I believe there is no need to preserve the many human kingdoms. All areas under demon rule can be unified into one nation, the Demon Realm," Shaquille proposed. "From now on, all ordinary humans will be classified as 'dust citizens', stripped of the right to have names and replaced with numbered codes. Only those who submit to the demons and make great contributions will become 'upper citizens', granted the privilege of having their own names and limited power to rule over the dust citizens beneath them."
If humans were to serve the demons, their "noble" titles would certainly need to change. How dare they call themselves nobles in the presence of demons?
Shaquille had long devised this system, even considering that human names might be troublesome and inconvenient for demons to manage, so he simply replaced them with numbered codes.
Thus, commoners and nobles were essentially just changing skins, becoming dust citizens and upper citizens.