Recommendations

girl cross-dresses as a man to get close to the person she likes

Sorry is an intense revenge melodrama with a touching love story. So Ji Sub is a handsome romantic, as is Ji Sung in Secret.

it has the same plot as it is all about the music industry, also in the drama you will find some famous k-pop idols (i will keep that a surprise)

the same story I koo gum is the thai version of bridal mask the same of some working in the army of the enemy of his country but he actually working for his country and he fall in love with someone who really hates and want to kill him for his betrayal for his country

They have similiar plots. In Happy Ending the father has cancer and prepares to say goodbye to his family. In Mama the mother is terminally ill and prepares to say goodby to her son. (and find a family for his son)

Both are adaptations of Jin Young novels though they are different stories. Both are the best adaptations of their respective stories. If you liked one you'll probably like the other but perhaps for different reasons. I highly recommend either for fans of wuxia series

The stories don't have much in common but I have read many comments (and I agree) finding the two male leads similar. It's true that they seem to have a cool and collected façade, but both have a very strange, irrational part to them that is revealed as they fall in love with the female lead. One of the most striking illustrations of this is their "demented" laugh. Also, both actors (So Ji Sub and Jang Hyuk) are more "mature" actors (37 and 38) that play mainly in action type dramas, and both Master's Sun and Fated To Love You are their first rom-coms in years.

Same cast ! I think George Hu and Annie Chen's chemistry is way better in Love, Now. Plus it's a rom-com.

They both got a lot of fighting scenes and about the main characters that begun from nothing became actors

both have the same theme. While IMAT working on incident case victims, DMAT working for both incident and disaster victims

IT ENDS THE SAME EXACT WAY FOR SOME CRAZY REASON. Except Gu Family Book doesn't have a sequel, neither does Rooftop Prince, BUT GFB NEEDS A SEQUEL. It kills me even now..

Because I feel like You Who Came from the Stars is the sequel to Gu Family Book I will never get to see...

Although I think Love Keeps Going is way better, both dramas contain the ups and downs of a relation, including the betrayal of a male lead. They both give off the same feelings, but the end of Love Keeps Going is a killer.

The plots aren't very similar, but when I think of She is Nineteen it reminds me of Shining Inheritance. Shining Inheritance is much better, but the feels are somewhat similar.