Both have FLs from the real world who enter a fictional historical world (novel vs. screenplay) and become involved with the story's villain, all while trying to survive the plot and return home.

Both dramas are about the FL entering a screenplay into a fictional historical world where she is a supporting character. The FL then tries to return to the real world by controlling the story and falls in love with the story's villain.

While one is historical and the other modern day, both dramas have a determined FL who is a single mother (either biological mother or aunt/adoptive mother) to a precocious little boy. The child takes a liking to the ML at the beginning and calls him his martial arts disciple. The ML has never met the little boy before but is related to him (father vs. uncle) and quickly steps into the role of father, all while falling in love with the FL.

It continues the series.
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Both dramas have a ML who is a supernatural creature (nine tailed fox vs. merman) and a human FL who accidentally kisses him and swallows his pearl/bead. In order to retrieve it before it kills her, the two end up living together, and fall in love.

Both are love stories between a mermaid or merman and a human. The mermaid/merman's life is attached to the human.

Both are short length dramas with a water being who ends up living with a human, and the two fall in love.

Both dramas are about a supernatural creature (nine-tailed fox vs. mermaid) who loses his spiritual object which becomes physically attached to the FL. While trying to figure out how to get it back, the two end up living together and fall in love.

Both are mostly light romances between a mermaid or merman and a human.
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Very different in plot and tone but both have mermen prince MLs who are a bit innocent at the beginning of the dramas.

Both are short length dramas about a merman ML and a human FL who end up living together. The ML is very naïve about the human world and requires the FL's help to obtain something so he can return to the ocean.

Both dramas are a mix of crime/mystery and legal genres involving a serial killer. Determining who is guilty and innocent is difficult at the beginning, with many twists in the plot. Both dramas have a similar tone/feel.