If you're referring to the Duke as the prime minister, no, he's not a real person/player. He's a character from the game
As far as I understood, the only real human there are the "Kings", their dukes and vassals are all NPCs.
The games is like empire vs empire where they invade each other and rise in the rank.
The Kings must also get the affinity of their vassals and dukes because if they failed to do so their dukes can kill them then they will have to start from the beginning again.
In the novel, it says they are real people since the player is now part of the world. The story is nowhere near the middle part of the novel. There's still a lot to uncover.
So, I m super confused about game thing. Is the prime minister also real player or not? Also, all the knights are npcs right? I cannot comprehend this game thing.