Both are mini dramas with a Republican Era setting in which the FL is out for revenge/to uncover the truth behind her family's death. She and the ML are both spies, something neither of them knows about the other.

Both are mini dramas in which the leads are assassins who are initially hiding their job from each other, believing the other is innocent. Both are historical settings, although different time periods.

Both FLs work in the fashion industry, and the MLs are intelligent but emotionally distant. The leads cohabitate (with or without contract marriage) and fall in love.

A:RTTF is the sequel to Alienoid.
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Both are about a Joseon era man who crosses over into modern day Korea and meets the FL.
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Both are short length dramas in which the ML(s) time travel from the Joseon era to modern day Korea and meet the FL.

Both are short length Korean dramas in which the ML from the Joseon era crosses into modern day and meets the FL.

Both are Republican Era mystery dramas with a policeman and a girl with an unusually strong sense of smell working together to solve cases.

Both are slow paced, poignant films about North Korean defectors. Both portray the MLs' relationships with their mothers.

Both are historical dramas in which the MLs are pretending to be eunuchs in order to investigate a case. The FLs learn their secret.

Both are historical dramas in which the MLs are pretending to be eunuchs in order to investigate a case. The FLs learn their secret.

Both are historical dramas in which the MLs are pretending to be eunuchs in order to investigate a case. The FLs learn their secret.