The actors who play the couples both have similarly great chemistry.
FL in both dramas are both capable and independent.
ML in both dramas are persons of authority who finds themselves exasperated by FL antics.

Both feature mermen as ML and takes place in a fantasy world.

Both FL are righteous and rather stoic.

Gender reverse of the plot with the love interest appearing to have a split personality because they are sharing their body with a demon half.

Both are about a supernatural and immortal man who ends up living and falling in love with an energetic actress.

Both feature male characters who take on cases that are normally taken care of by the police or private investigators, and solves them by underhanded means.

Both are about a talented ML who are socially akward (in the case of Love and Redemption its because the ML has a stutter) Both ML are prohibited by their master/sect from associating with women

Both are about a male lead who are obsessive in their love for the FL.
Also they are both pretty weird intelligent guys with glasses.

• Both dramas have a ML that are an overbearing CEO who manipulates and schemes to get the FL into a relationship with them.

• Rich Man and Poor Woman in both

• Boss/Employee

• The FL of both also have a short temper and despite their slight builds can be strong enough to take down grown men.

Both dramas are about a fox demon who has cultivated for centuries but their goal is thwarted and they end up being involved with a human who becomes a romantic interest.

Both dramas feature a ML that is a Nine-tailed fox though Tale of the Nine-Tailed focus more on serious drama rather than comedy.

Both contains black comedy elements juxtaposed against the lighter elements of the story

Both Mk are essentially nice people

Both dramas involve

* the ML and FL having to pretend to be a couple in front of family.

* a resourceful heroine

* a couple having a bickering relationship with great chemistry