Both stories share a ML that does shady things for a living, but are sweet hearted at the same time that they would do anything to protect their loved ones even start a rebellion (like in rebel: thief who stole the people).

Also in both the king has a unstable state of mind, gets manipulated by a woman and had daddy issues...

The vive in both is really positive, the protagonists are always plotting something but for the grater good and against of the evil power.

Even one of the main songs that come from the Joseon era folklore is present in both, in one sung by a woman and in the other by a man.

In both serial killers have destroyed the protahonists life and the couple investigate together the crimes.

The investigation is the centre of both of the shows and there are some surprises that nobody saw coming in neither of them.

You have single mother's fighting for their future in both.

In both male leads fall in love at first sight and both are really optimistic and hardworking.

Both dramas have this great feeling and healthy relationships in their couples.

In both there is a serial killer that is involved with the female lead.

Both male leads are gentle policemen that face their problems at the same time they fall in love.

In both there are amazing support roles that make the story more lively and funny.

Family bonds and mothers with mental deseases are present in both too.

Both deal with single parent homes and difficulties that they face when it comes to relationships.

The soundtrack of both have a unique vibe that transmits a lot through the scenes.

They both have sweet but strong male leads that make you change your idea of the perfect man.

Both dramas are connected with work issues and the career of the main characters.

The couples have a strange connection that trascend ultimately the work environment.

They both have the same vive and fresh feeling with many charming support roles and funny scenes.

The characters have the same age, and they face problems related with their jobs and carreers.
The couple know eachother for a long time and its after some events they get to love eachother.
Some characters are really dense and funny at the same time wich lead tho many hilarious secenes.

Both dramas have similar fresh feeling and a great balance between love and work issues.