Both are lighter historical dramas with a similar tone and pacing. The FL ends up in another girl's body and lives her life, and the ML is ill or cursed and initially stand-offish/cold.

Both are lighter historical dramas in which the FL ends up in another girl's body, living that girl's life, and still sees her in dreams/illusions for much of the series.

Both are lighter historical dramas in which the FL enters another girl's body and takes over her life.

Both are lighter, fluffy historical dramas with the FL entering another girl's body and having to live her life.

Both are lighter dramas with a FL who enters the body of a girl who has died, taking over her life. ML suffers from some medical condition,

Both are fluffy historical set dramas with a poisoned ML and a cutesy, upbeat FL who is from a different time or culture.

Both dramas have FLs occupying the body of a different girl.
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Both are mostly light, historically set dramas with a ML who is poisoned/different and lives mostly apart from other people until the FL crashes into his world.

Both are fluffy, historically set dramas with a ML who is poisoned and an upbeat, cutesy FL.
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Both are fluffy, historically set dramas with a ML who is poisoned/not expected to live long and an upbeat FL.

Both are fluffy, historically set dramas with a ML who is poisoned/not expected to live long and an upbeat FL.

Both are short length dramas with the same actor as the ML and a FL from the modern, real world who enters a story set in historical times and becomes a character there.