Both involve the lead, who is viewed as unattractive or lacking in confidence, changing through the help of an ordinary but magical object.

Both MLs have been poisoned, resulting in them becoming violent and animal-like during the full moon. Both FLs have another girls face and identity and are with the ML for a personal goal/reason. Both dramas begin with the ML in his poisoned state attacking the FL.

Both are mini dramas by the same director/writer and with the same actor as the ML. While they take place in different eras, both are historical and beautifully done.

Both are mini dramas in which the FL is a spy who marries the ML on a mission. Unbeknownst to her, the ML is also a spy who wears a mask who she has fought with before, but he is now pretending to be weak or out of his mind.

Both are historical dramas in which the FLs have the skill to change faces (either their own or the faces of others).

Both are historical/fantasy mini dramas in which the FL is able to or is forced to change her face, and she then marries the ML in the place of someone else.

Both involve multiple worlds/stories in which the leads can and will meet. Both have a guy who is a "guide" sort of figure with blonde hair who knows he truth behind their lives, and both FLs have a heart condition and aren't expect to live long but fight against their fate.

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Both are historical mini dramas with a strong FL and a seemingly weak or foolish ML who is hiding a secret powerful identity behind the mask. The couple is forced to marry at the beginning of both dramas.

Both are historical dramas in which the ML is poisoned and the FL a strong fighter. The two marry at the beginning of the drama and later fall in love.

Both are historical dramas. Both MLs have a powerful secondary identity but are weak and ill due to poison.

Both are historical dramas in which the ML is weak and poisoned. The couple marries early in both dramas.