Recommendations

As The Red Sleeve doesn't show much of how a King's grandson was the Crown prince instead of his father, a fan of The Red Sleeve can watch The Throne to understand more of the situation.
For the Throne fans, they can watch Red Sleeve if they want to know the story of Sado's son. Red Sleeve is the show they should watch if they want more focus on Sado's son's romance. There is also some politics in Red Sleeve, but the love story has a bit more focus (especially the last 2 episodes).
In contrast, the 2007 drama Yisan tends to have more focus on the accomplishments of Yi San as Crown Prince then King (though romance is also important in this show).

Yi San is a 2007 drama about Sado's son. It covers about the same time period as the more recent Red Sleeve 2021 drama except that it has greater focus on politics. If you want to watch a drama which shows more focus on Sado's son's politics as a prince then as a king, Yi San 2007 drama is the show for you. Yi San 2007 also shows more on how Sado's son was acting as his father was dying in the beginning episodes.
For Yi San fans, you can watch in The Throne another portrayal of how Yi San's father died.

The whole vibe of the dramas are very similar. From two young school kids with aspiring dreams to the longing of one having a crush on the other while the other is clueless are very similar. The scenery, the screen filter, aesthetics, the beach settings everything reminded me of the drama. I felt similar feelings while watching the drama

- TVN dramas
- Fantasy k-dramas
- Based in a fictional nation
- great fight scenes
- amazing storylines
- incredibly talented actors
- have 2 seasons
- a lot of characters (multiple main roles)

Both are high budget fantasy korean dramas released in tvn. Both dramas have amount of great CGIs, unique plots and incredible acting.
Both dramas set in fictional countries. Both ML characters has birth secret with prophecy.

Like We Best Love: Fighting Mr. 2nd, Be Loved in House: I Do is an office romance. In We Best Love, Zhou Shu Yi and Gao Shi De were past lovers who were brought back together because of a business deal while in Be Loved in House: I Do Jin Yu Zhen and Shi Lei love blossoms from hate to love boss-employee relationship.

Sun owns a coffee shop and hires his brother's friend Mork to work with him and eventually become a couple. Although Sun and Mork are a second couple, their story takes place mostly at Sun's coffee shop. Coffee Melody has the same coffee shop vibe.

It tells the story of Woo Hyuk back when he was in high school. We see a different image of him. The romance is also different from the prequel.

It's another HYBE's survival show. K, EJ, Nicholas and Taki previously took part in I-LAND. Also Enhypen, which was grouped togehter in the I-LAND, made a guest appearance in the first episode of &Audition.

This was the first show that came to my mind after watching a small part of EXchange on Insta. They literally have the same theme, of putting some people somewhere so after a certain period they will have to choose a partner. The difference is in that in Singles inferno that somewhere is a desert and the people are complete strangers.

The first season of the same show:)
I also haven't watched the first season, but from the first two episodes I got to understand that the overall rules and the main mcs are the same.

Both dramas are about a rich ML with trauma entering into a contract marriage with the FL.
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MLs end up entering into marriage with the FL due to an agreement/debt between their families.
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MLs are rich CEOs with trauma who hire the FL (contract marriage vs. bodyguard). Both dramas have a similar tone and feel.

Both MLs are rich with trauma triggered by something specific (crowds vs. water). FL is a poor but spunky cartoonist.