Both leads grew up together, are best friends and end up living together. Both couples have feelings for one another. The only big difference is that in I need Romance 2 the couple already dated before.

Best friends grew up together, their professions are helping one another and slowly they start to realize that they mean more to one another.

Best friends, that grow up together realize as an adult that they mean more to one another. In both dramas the male lead realizes his feelings first and the female lead slowly realizes them too. Cute dramas about a similar topic.

Best friends to lover trope. Something happens and they have to sort of live together and slowly feelings get revealed and confessions made.

Best friends, that grew up together, live/start to live together and that feel more for one another. Both stories are quite similar, the only big difference is that while More than blue makes you get out a big box of tissues, Soundtrack draws a big smile on your face

A pair that has an instant connection. A hate relationship that turns to romance. One (Liar) or both (Before we get married) that are in relationships and face infidelity, while being engaged to someone else. And fiancé(s) that cannot let go.
Both dramas are nearly the absolute same story.

Both dramas are about a crime that is connected to someone on the police force.
In both dramas the officers know the suspected culprit well, are estranged from them and are now involved in their cases. Both keep secrets from their colleagues and both dramas have the subject of poverty, abuse, suicide and bullying.

Extreme bullying and victims taking their revenge in a specific way that is in both dramas similar. Both dramas also have the theme of mentally unstable people and both dramas are filled with twists and surprises.

Both dramas revolve around profiling and deal around the psychology of crimes and culprits. The only difference is that while Through the Darkness focuses on the detective trying to figure out the criminal, while in Burning Ice multiple different people try to analyze one another and their opponent. Also, both have very well concepted crime cases.

Both dramas deal around the concept of artists that paint and help solve crimes with their skills. While Sketch has a supernatural aspect to it and Under the Skin focuses on a forensic artist, they both are very interesting and follow unique concepts.

Basically the same story but different settings. We have an age gap romance where the woman is older, both couples end up working together, in both dramas one of them is the boss of the other, and many other aspects that would be a too huge of a spoiler.

Both dramas are about an amnesia story where the female lead finds out she is married/the fiancé of a guy. Said guy tries to be understanding and helpful of the girl, however something seems suspicious about him. Both have very well done story twists that one does not truly see coming.