from what I got, Lord Baeksa is a ancient dragon (?) that possessed the body of a prostitute, the tall guy is his bodyguard that cares for the body of the prostitute (since he took care of him when he was a child). They're still living in the prostitution house (idk, English's not my first language) because Lord Baeksa has to solve a pendent matter in regards to the bodyguard (to be able to fully use his dragon powers and leave the house) and the guy doesn't have the strength to give up on the thought that the prostitute might return to the their body if Lord Baeksa leaves it (and that's ehy he accepts to be his bodyguard).
Thank you for your response I understood that part I was talking about the story. When they people ask him has he heard the childhood story about the dragon and what transpired.
In Korean folklore Imoogi are a stage of pre-dragon ascension. The story is about a dragon who was ripped in two for his sins, his physical body consumed to stop his resurrection which made him become an imoogi. If Baeksa is the dragon in the story then after his soul escaped its seal, in his weakened state he took over a human vessel(which was possible only because the original body went through so many terrible things it "lost its soul" and became an empty vessel) and is now currently trying to fully merge with said body so he can cultivate to ascension(dragon form) again.
We don't really know what's going on with Muyeon and his obsession with his sworn father(Yehwa). Yehwa was a male kisaeng(courtesan), basically a slave who couldn't escape his horrible life, who decided to take care of a child. We basically just have bits and pieces rn so we don't know what the horrible thing Muyeon did was, nor what their full circumstances were
Can someone explain the story to me like the hundred year old tale. I'm confused when the story was being told I try to follow along but when stories start using historical metaphors & verbage and such I get lost