The Dreamlike Seal (2021)

They are similar and both are filmed horizontally. Although I don't know much yet, what I do know is there are upcoming seasons for Psychic Princess.

FL ends up unexpectedly married to the ML, which grows into love. Both are enjoyable fast-paced historical romances.

FL switches identities with another girl which results in her becoming the ML's bride. The two end up falling in love.

Forced marriage turns into true love (in TDS the bride is switched, in GL its the original bride). Both have the same actor as the ML and are historical romances.

Both are about the FL switching identities with another girl which results in her becoming the ML's bride. The two end up falling in love.

Both are short and sweet historical romance dramas in which the FL ends up entering the ML's family under a false identity, but the two fall in love.

One is the original drama, the other a short epilogue to the drama.
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Both are historical romance dramas in which the FL ends up entering the ML's family under a false identity, but the two fall in love.

Both of the drama are very similar :
-Both of the FL and ML are very strong
- Both of the drama are short but TDS is bit too short but is worth watching
-Both of the FL and ML are trying to hide there real identity
- Both of the drama are historical
-Both dram the FL and ML are married
- Both of the FL and ML are Skilled Killer
- Both of the drama romance is GOOD
I suggest you to watch both of the drama but one difference is TDS is vertical filmed whereas TKIAR is filmed normally.
ENJOY :) !!!