The Red Sleeve

If the drama is as much based on the novel, the ending of the ml and fl of Scarlet Heart and Red Sleeves are same. Regardless of the time travel in SH:R, the story flow of political reasons coming in between lover and separation are same.

both are saeguk and have beautiful cinematography , the chemistry between leads is perfect and would make you wanna continue for hours

Both are essentially about court ladies who try their hardest to protect the king and support his reign.

The shows give me similar vibes because of the somewhat taboo or forbidden love. Also, the pain and angst. The cp in OnO doesn't argue like in the Red Sleeve, but the apparent love but not admitting it at first is the same.

Yi San, later King Jeongjo (Lee Jun Ho) was the son of Crown Prince Sado and grandson of King Yeongjo .
So, if you want to know what happened between Crown Prince Sado (Yoo Ah-in) and King Yeongjo (Song Kang-ho) then this is the movie for you.

In both dramas the couple is very much in love. They also are both based on real stories. In both "The Red Sleeve" and "Queen for Seven Days" the couple has their ups and downs, disagreements, farewells. But they always love each other, despite the tragic circumstances.

This drama could be considered an introduction to King Yeongjo of Joseon, grandfather of Yi San. This prelude can explain many of the turbulences that are depicted in The Red Sleeve, King Sukjong effected many changes that impacted Yi San's rule

Lee Se Young is the main Female Lead in both dramas
Somewhat similar vibes but are pretty different plot-wise.

*In both dramas, there is a power difference between the ML and the FL. *

MAIN PLOT:
-In The Red Sleeve there is love between crown prince (ML) and a court maid (FL).
-In The King's Affection it's the opposite. The FL is disguised as a man and she is also the crown prince who is loved by the royal tutor, who is our ML.

SIMILAR TOPICS OF:
-Childhood nostalgia
-Difficult and abusive family relationships
-Political drama
-Injustice in Joseon; class problems and gender inequality
-Love between people from different classes.
-Multidimensional characters with their own ambitions.
(All of these topics affect the relationship of the FL and ML. )

DIFFERENCES BETWEEN DRAMAS:
-The ML in the Red Sleeve is way more toxic, and the FL is more often helpless despite her clever ways. It can be fun to watch toxic couples, it is like a guilty pleasure but this couple was unusually toxic, in my opinion.
-The King's Affection has a bit more humor. The FL is quite amusing as the 'cold ice prince' while the ML tries to assist her. His love is more pure.
-Overall, The Red Sleeve is more sad and tragic because the FL suffers a lot and she is way more helpless. The FL only wants to be able to make her own decisions. It's realistic, I guess... But it made me cry more and not laugh as much as in The King's Affection, despite this series having a few slow episodes in the beginning.

If you like one of these, chances are that you'll like the other one.

Kinda similiar vibes, male lead is crown prince and kinda feels in bith thats its forbidden love. Both princes kinda have similiar personality so far. Also both have little comedy.

Both are sageuk dramas, fictionally developed but with real-life events. It has a beautiful love story between the leads with a bittersweet ending. Deok-Im and Ae-shin are both strong and independent female leads.
Both women are willing to give up love for their principles and the life they want. The Red Sleeve occurs "before" Mr. Sunshine according to the chronological order. Mr. Sunshine takes place shortly afterward the American-Spanish War, during the Japanese occupation of Joseon, and shortly before World War I.
They have a bittersweet ending, but with a beautiful romance. Each character has a well-defined personality and a male lead who is willing to support the women they love even if it meant letting them go so they can fulfill their dreams. Two people who loved each other deeply and always wished their significant other to achieve whatever they wanted even if it conflicted with theirs.

In both dramas, the main female lead (FL) is a spirited woman allowed a lot of freedom who falls in love with a prince in disguise.

In both, when the FL realizes the horror of what she's getting into, she tries to back out, compromise, run away from her fate. In both, these attempts are rational, understandable and deeply empathetic. In both, the FL has much more to lose than the prince.

On the other hand, Good Bye, My Princess is darker and more sure of its themes than The Red Sleeve, and it centers the main FL's troubles and sacrifices all the way until the end.

This show is a spin off of the korean drama "The Red Sleeve" (2021) from MBC, where you can watch the main cast having fun and making comments about stories from the behind the scenes and being playful.

In 18th-century Korea, Prince Yi San is a perfectionist haunted by his father's murder. He's set to inherit the throne once his cruel grandfather, the current king, passes away. Despite the emotional scars left by his father's death, Yi San aspires to be a benevolent ruler who reforms the kingdom's laws. At court, he encounters Sung Deok Im, a spirited and intelligent young woman. While Yi San falls in love and proposes she become his concubine, Sung Deok Im grapples with the restrictions and responsibilities that come with royal life. However, as their love deepens, she begins to see the potential to bring positive change to the troubled realm through their union.

=> Both are retellings of the love story of King Jeongjo and his beloved concubine Royal Noble Consort Uibin Sung (her real name is Deok Im but she's called Song Yeon in Yi San).
=> The court lady is shown to have a special talent (painter in Yisan, storyteller and writer in Red Sleeve).
In my opinion, Yi San should be the top recommendation for Red Sleeve fans, come on people, they're both MBC dramas about the story of one of Joseon's best kings and his beloved concubine.