My Decoy Bride (2023)

Both FL and ML are assassins and hide their identity in the first part of their marriage. They both work for the same organization and FL is tasked with killing ML which she thinks the easiest way to accomplish is to marry him and thereby entering his mansion. It is also a romance since the two of them fall in love with each other.

Both are historical mini dramas in which the assassin FL infiltrates the ML's home in order to kill him, but the two fall in love.

If you enjoy these bite-sized costume dramas but trying to sort through the gems from the rubbish, A Familiar Stranger is among the best of the genre. Like My Decoy Bride, one of the main characters recognize the other from a past encounter, and while the circumstances that lead to the marriage are different, the FL also has a false identity when she marries the ML.

Both are historical mini dramas with a tough FL and a ML who pretends to be foolish.
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Both are mini dramas with rival assassins who marry each other, with each unaware of the other's secret identity.

Both are historical dramas in which the couple briefly met years before, leaving an impression on the FL. Later on, she accidentally marries the ML, joining his large house, and discovers he's now foolish/pretending to be foolish.

Both has
Masked hero

Strong female lead

But LLWJ might feel slower if you watched this first but otherwise will enjoy