Both have a modern day FL transported to the past and a ML who is supposed to only have a short life.

Both are mostly fluffy dramas with a poisoned ML who can only be saved/cured by the FL who comes from another world.

Both are shorter dramas with a poisoned ML who the FL is the only one able to cure him. In both, the ML falls first.

Both have a poisoned ML that only the FL can cure/save.
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Both dramas are about a terminally ill FL who falls in love with the supernatural ML Both MLs undergo occasional transformations into monstrous beings with bloodlust. Both MLs have an overly protective male friend who resents/distrusts the FL and tries to keep them apart.

Both dramas have an alien ML with powers and an actress FL. Both romances are star-crossed, with one or both of them risking their lives to remain together/on earth. LAFT even references MLFTS in episode 4.

Both are movie length stories featuring a celebrity FL and an alien ML with special powers that he uses to help her. The ML's life becomes tethered to the FL's in the process of trying to save her, and he risks his life to remain on earth. Both MLs have alien friends who try to persuade them to leave the FL to save their lives.

Both dramas have a plucky human FL and supernatural ML who has special powers and a monstrous side/appearance who met the FL when she saved him. Both FLs have affectionately insulting nicknames for the ML ("monster" vs. "big weirdo").

Both have a terminally ill FL who in their lowest point crosses paths with the ML who is a supernatural being and aids them in someway.

Both feature a time slip bringing the leads, who are a few years apart, together, and results in them having to cohabitate. Both stories have a similar feel and tone.

Past connection between the main couples, ML is formerly a deity, now on earth without his memories/powers. Both FLs are more innocent characters who due to their professions or illness are initially outcasts in their town. Both dramas have a similar tone and feel with light xianxia elements .

Both couples knew each other as supernatural beings before and are now reincarnated with no memories when they meet again. Both are xianxia dramas in which most of the story takes place in this world.