Recommendations

Both are historical dramas in which the ML is ill with a short time left to live that he then shortens saving the FL. They are weak physically but strong mentally and in both dramas are involved in the power struggle for the throne. Both MLs are doctors or work as doctors for a time. Both FLs misunderstand and are separated from the ML for a long time.

Both have a similar plot of the FL marrying the prince who then becomes the emperor. Both FLs become trapped between the two royal brothers as well as the emperor's evil concubines. Both FLs lose at least one child due to the emperor, and are believed to have lost their fertility as well (in the movie BCTSAL the FL learns she is pregnant again). A lot of both dramas are set within a palace and the FL undergoes a lot of hardship and emotional growth.

The supernatural experience in the medical field is present in both creations and the idea of crime and the supernatural helping to solve the conflicts surrounding the hospital's administration or higher ups.

Liar game is a japanese drama with a lot of mindgame, if you liked Squid game you should really watch Liar game.
Both have a similar plot, it's money game ruled by secret organisations where you can finish rich or.. you know

The female lead in both the dramas suffer from inferiority complex about their appearance. The male lead falls first both in mask girl and true beauty:)

When I first saw Something About 1%, I was so pleasantly surprised by the female lead character. Even though she was "poor" teacher (in comparison to "rich" CEO heir), she was not the usual cliché. She was smart, strong, no nonsense woman. Here the FL is the same and they both did not let the rich guy's mother/aunt/ex scare them. Just the opposite....

One is the drama, the other the finale movie which gives it a proper ending.
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In both series the characters work in an office. In both series one of the characters is trying to ignore/move on from the love they feel.
In both series the chacters are nice and they make each other happy and healthy.
Both series have simple plots and they are short.
Both series focus heavily on the two male leads and their story together, we dont get to know anything really about family or friends.
These series give off similar vibes. They are feel-good and sweet but they have some depth to them.

Both share a FL running an inn/boarding house, a ML who lost his father which causes him to hide his identity, & a family secret.

While this one seems more lighthearted in a way, Come and Hug me has the same FL lead and its crime heavy. While there is not time travel involved, I think the style and telling of these dramas are similar. Come and Hug Me is a more angsty slow burn however, I think they are pretty similar so if you haven't you could always give this one a try!

It's all about first love. Both of them met in the young age and they started a beautiful story of first love. They were both also separated from each other because of unexpected factors in their life.

The difference = the adult version of 2521 didnt meet and it wrapped up as first love story without reunion. Hatsukoi got happy ending and both of the leads are ended up together.

Both are fantasy/historical dramas with a older master ML and a younger disciple FL. Both MLs are cursed/harmed in some way (a cold curse vs. a wolf curse), and both FLs start out very innocent and then experience a lot of grief and loss.

Both are historical/fantasy dramas in which the ML is poisoned/cursed resulting in an animal-like personality to emerge.

Both dramas involve characters under a "wolf" curse that takes over their personality. Both also have a star-crossed romance between the leads.

Both sageuk portrays independent FL falling for the ML without knowing their real identity, and has very interesting characters and relations surrounding them. Also includes the unavoidable political plotline every historical drama has. There's a good balance of humour and seriousness.