TLDR-
You may expect the normal melodramatic saquek, but this drama will surprise you.
Gorgeous OST, beautifully shot cinematography with layers of deeper meaning that'll break your heart when you're paying attention; a strong plot that doesn't meander, and very strong acting throughout to keep it all seamlessly tied together. Even saquek-tired viewers will be pleasantly surprised by this fresh, even modern take on a real-life story.

Thoughts on the main leads:
Lee Jun Ho: I've been a devoted Lee Jun Ho fan since watching his first main role in Just Between Lovers. I first watched that series because I really liked the premise and the cover photo, and quickly became utterly enamored by Jun Ho's character. He was charismatic, deeply troubled, and full of old physical and emotional scars that drew me in throughout the entirety of the series. The arc between him and his grandma crushed me and I thought his emotional scenes were masterfully done (including his public breakdown in the street when he received his diagnosis). I had no clue he was an IDOL until I looked him up afterward and saw that his real-life persona couldn't be more different from his character in the series, which impressed me even more. From then on, I was a huge fan and looked forward to his other roles. His charisma certainly knows no bounds and is not limited to 1 genre. He portrayed his role as the crown prince (and later as the king) masterfully and I can't help but replay his emotional scenes over and over. His relationship with his grandfather, the king, was troubled and full of complications that I enjoyed watching play out on screen. It teetered so often on domestic abuse with the emotional and sometimes physical warfare the king inflicted on him, despite how often he claimed to love him. The dynamic was interesting and effective and I found myself both angry at the king and full of pity. In the end, I could sense the raw loneliness, grief, love, and pain Yi San felt for him.

Lee Se Young: Although I'd only seen Lee Se Young in another saguek, The Crowned Clown, that series also happens to be one of my all-time favorite KDRAMAS so I had high hopes for her. Her role in The Crowned Clown was much meeker in character, and I actually thought her character took away from the overall plot and pacing of the drama because I thought the most interesting aspect of that drama was Yeo Jin Goo's Clown Ha Sun and King Yi Heon and when the romantic melodrama aspect started taking the forefront of the drama and pushing the suspenseful dynamic of the twin brothers to the background, it changed my overall interest in the show (although I still loved it for different reasons). Her role in The Red Sleeve is much more prominent and gives her a lot of room to stretch her acting skills, both emotionally and physically and in different genres, so I especially loved watching her this time. Her facial expressions are so emotive and I found myself laughing and crying with and at her on several occasions.

OST: Gorgeous. Emotive. Enhanced every scene without overwhelming it.

Plot: Surprising and fresh with subverted tropes, strong and empowered female characters, broken stereotypes (female saves male MULTIPLE times, female with strong willpower, sensitive man, etc). I loved Deok Im's strength as a woman in her determination to live for herself, regardless of the pain she'd feel by not going the easy route. I loved that she saved Yi San and was able to protect him on multiple occasions. I loved Yi San's consideration for Deok Im later on in his conviction to treat her as a woman and not as an inferior subject. I loved Yi San's royal guard and his adorable gullibility and fierce loyalty. He brought on moments of much-warranted levity which brightened both the scene and Yi San's countenance. I loved the friendship between the court ladies and the moral greyness of some of the other women. I loved that the "antagonists" in this drama wasn't the true villain; it was the palace and its rules that entrapped our main characters and the "heroes" were the very people that were pillars keeping the palace living and breathing.

Episode 14 Update:
I've grown very frustrated with the relationship between Yi San and Deok Im.
I understand there are many complexities, and I empathize and understand Deok Im's fears and insecurities toward accepting the role as a concubine so I can't fault her for refusing the role and putting herself first; however, Yi San has only ever been fully honest with her regarding his feelings and his desire to keep her safe whilst she's *brutally* turned him down so many times, I've lost count. She disregards his feelings to intentionally hurt him and push him away despite her true feelings, and she only ever treats him for his title and not as a man. Yi San frustrates me as well because he's so painfully aware of his title, that his desperation to be treated as a man by Deok Im understates how serious and challenging that request would be for a normal person to hear. All physical skinship, excluding the reuniting hug, after she saved him from the ambush, has been physically forced and one-sided, including the kiss at the end of Episode 14. If I'm being told to believe she wanted that kiss because she submits into it at the end, no thank you k-drama world, that's not how reality works. I'm frustrated he did that, and I'm frustrated that it was *once again* a one-sided show of affection (that she didn't even ask for). I want to see HER fight for him *as a man* just 1 time and she hasn't. It has only ever been for her king and highness (excluding the time when they were children), and I pity him for that (despite disapproving of his behavior toward her physically).

Episode 15:
"I have deceived his Majesty. His Majesty may deceive the court ladies at his will, but a court lady may not deceive the King."
UGH. Still pretty frustrated with their relationship. They're both in very difficult positions, both on the level as a man and a woman and as King and court lady. I selfishly really just want her to hug him and tell him she cares about him too and he's not so painfully alone in the world.


Epsiode 16 & 17:
Oh. My. Tears. What a heart-breaking, gorgeous, beautiful, punch in the gut.
I love the ending so much. I love the subtle and nuanced cinematography that captured so elegantly the "prison walls" that framed so many of our characters throughout. I loved that Yi San stripped away and laid himself bare for Deok Im and that she *finally* openly acknowledged her love (and without saying it still) for him. I loved that they ended up together and both willingly chose the other in the end. If I'm not making much sense atm, it's because I'm still typing through my tears.

Can't recommend this drama enough, and I'm so happy our beloved cast and crew received the proper attention and accolades that were well deserved.