After watching episode 5 with eng sub, here are my thoughts/speculations:
1. How refreshing indeed that dongju is aware of nokdu liking her. I really really like this side of her. Despite being in joseon area, she's quite advance and matured. From her perspective, she believes nokdu has a lover of his own, i love how she makes sure nokdu aware of his "flirtation" in view of his situation - "How can you be smiling like this to me?" or "stop being nice to me". Dongju is someone you can trust not putting herself in a third wheel position.
2. Also love the fact that Dongju is straight forward and does not push around the bush, wanting to confirm Dongju feelings for him.
3. I have a feeling the king's son maybe Hwangtae (nokdu's brother). Somehow his character not yet standout and thus far we don't know anything about him.
4. Dongju is not Dongju's real name right? She has a different name when she was younger (she was daughter of a noble family, or maybe even daughter of higher up in the palace) i remember her mother was calling her Eun Seo. I believe Dongju is her gheisa name. But i do wonder why CYM calling her Dongju instead of her real name.
5. I wonder if the king son incident relates to the massacre of dongju's household.
6. I was not so happy with the kiss scene, it looks like typical idol kiss (where mouth touch mouth and no other movement...awkwardddd)
7. I heard that CYM is a new added character for drama only.. so far i have not seen any dynamic purpose of this character yet... beside being added as Dongju's childhood friend and a bait for us to see nokdu jealousy.
Not expecting a wow writing, but like others have pointed out, the flow of the drama is getting a bit more choppy these recent episodes. Nevertheless I keep on watching because of the casts.