I liked the mystery. I have been watching historical dramas, but this one is different. As usual " Ireine Song" did her job. First time seeing "Sun Zu Jun", very mature acting, he has a good future. In a few places, I thought "Ding Ze Ren" was a bit lacking, as a new face he has done pretty well. The overall mystery part of the story kept me on hold, more than the main lead's emotional bond I liked the second lead's emotional part and bonding. But the drama didn't disappoint at all.
Didn't expect this from "Choi Dae Hoon", such a dynamic actor, excellent! Also "Shin Sae Kyeong" expressions were too good. Good start, hope upcoming episodes hold the same expectation.
The actors/thriller are all good, but I am not buying the reason, at least in Asian history, there is no such relationship, if it happens, they would be killed by the village people on the spot, so rated it 5
Finally, Wi Ha Joon is the main lead, I always think his acting skill is wasted. I watch "Worst of Evil" just for him. What a composed and calm acting, damn good, very talented actor.
Good Thai Drama so far what I have watched. Ryu Vachirawich Watthanaphakdeephaisan's acting skill was so mature, looking forward to his other projects.
K-Drama 
Ireine Song" did her job. First time seeing "Sun Zu Jun", very mature acting, he has a good future. In a few places, I thought "Ding Ze Ren" was a bit lacking, as a new face he has done pretty well. The overall mystery part of the story kept me on hold, more than the main lead's emotional bond I liked the second lead's emotional part and bonding. But the drama didn't disappoint at all.