Wo De Jiao Ren Di Di (2023)

Both are mini dramas in which the human FL encounters and ends up living with the ML who is a merman.

Both are historical mini dramas with a strong, domineering FL who is poisoned and a ML who she keeps as a slave/servant.

Both are mini dramas set in a world where merfolk are mistreated and/or hunted and involve a relationship between one of them and a human detective.

Both are historical fantasy dramas in which the FL is poisoned and the ML is an imprisoned merman who she rescues and "tames".

Both are about a captured merman and the relationship that develops between him and a human.
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Both are about the relationship between a human and a mermaid/merman.
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The FLs have a similar personality, both MLs are aquatic creatures, and both the settings/tone have a similar feel.

Both are about the relationship between a human and a mermaid/merman who they end up living with.
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Both are mini dramas in which the human FL encounters and ends up living with the ML who is a merman.