I would say it’s more going for mortal human (Muyeon) x immortal being (Baeksa).
Each one have some hardships to overcome but slowly they will see that the only solution is work together,
I could see how that might be compelling but I stand by the guard x lord.
Mainly because that's how they are both treating their relationship. Baeksa is quick to dismiss a human servant, putting responsibilities and desires of his own and of an imoogi before anything else, and Muyeon; the guilt riddled but selfish guard who cannot decide between duty and self-interest.
The only reason why Muyeon is guarding Baeksa is 'cause of his ties to Baeksa's ascension.
Baeksa isn't a lord, either. He's more akin to a lesser god since he's supposed to be an immortal dragon. He doesn't have human status so he gets what he wants via deadly force that humans cannot combat against.
The plot is good enough if you don't try to compare it to the 50,000 other period pieces that center around a lord and his lesser.
Hope that helps.
In their social, human, context Baeksa is a lord though. Even with the rumours and stories that follow him he is treated as such.
Without comparison it's still boring, which is fine for anyone to think, just as it is fine for anyone to enjoy it. Just in case you needed clarification.
To get the good things out of the way I enjoy the, loosely, period appropriate language used by everyone, feels far more like a period piece than most historical manhwa I've read. The art is also quite enjoyable.
The story itself... leaves much to be desired. It seems to be going for your somewhat standard guard x lord trope but misses, in my opinion, a lot of the intricacies that make that trope so enticing to read. (This could be an attempt at subversion that I just don't enjoy.)
As a reader I can't help but feel, suddenly, a little rushed by the pacing; like a lot is going on but not quite grounded.
Obviously, with it being so early on in the series, I can't fault it for not sharing all details that are yet to be revealed. But I do personally feel, I have not been given enough time with our leads to care or root for either Muyeon or Baeksa. Which is a little sad to say, seeing as they're basically the only characters the chapters have been focused on thus far.