Both have a lead who magically and temporarily transforms into completely different people. The other lead has a special connection to them and learns their secret.

Both have a lead (ML vs. FL) who magically transforms into different people on a schedule(every day vs. every month).

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Both are movies in which the ML is trapped in some odd form of time (a loop vs. non moving time) that he thinks is just him until he discovers the FL who is experiencing the same thing. Ultimately, it's revealed that the FL triggered it due to a health-related thing that makes her unable to move on.

Same story, different adaptations.
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Same story, different adaptations.
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Same story, different adaptations.
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Same story, different adaptations.
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Same story, different adaptations.
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Both are mini dramas with an assassin FL who marries the ML under false pretenses in order to complete her mission.

Both are mini dramas with an assassin FL who marries the ML under false pretenses in order to complete her mission.

Both are mini dramas in which FL is a writer of a historical novel and the ML is a character there who magically comes to the real world, appearing in the FL's house.