NEED HELP FINDING MANHWA

i remember seeing a tiktok rec of it but i have no idea where that video went
All I remember is that the mc was a normal guy who got reincarnated into this other guy (could be a villain) and I think he has a reputation for being cold or stoic (might be a duke or mage or demon not sure??) and he has short blond hair
The one scene I remember is when the mc (in blond's body) was reintroducing himself to his servants and he was like "hii!" and friendly, which made the servants shocked
I think the mc's soul was summoned to the other world because his soul was the most similar to the og blond's soul. only the closest servants know about the mc's situation and they're in a contract or something to fufill the role of the og blond so he has to undergo classes to learn to pretend to be him
Its also a historical fantasy manhwa, I believe it's NOT a BL but I could be wrong
Ik its not a lot to go off but if u got a clue pls help me PLEASE.