Palace arranged marriage. Right from episode 1. Male Lead is cool calm, strategist, fights well and warrior at battle field. Male lead doesnt put much thoughts into marriage nor male-female relationships. Male lead is guarded against female lead, distrustful at the start, knowing female lead was planted in thru marraige as a spy for the enemy (palace). Female lead has own opinions, strong will but crafty enough to survive. Lively, and lovable. Female lead who is more physically affectionate and vocal about how they feel, including confessing to Male Lead first
Marriage then divorce. Secrets and fantastical elements. Heart wrenching moments. Great otp and chemistry.

Similarly a C drama on sports and romance. Both focusing on swimming and competing. My Mr Mermaid is warmer and has other lovely aspects of friendship, and team spirit.

The same scriptwriter Yang Hee Seung penned both dramas. Both dramas have wholesome memorable characters and comedy within quirky romance. Oh my ghost has extra elements of ghost mystery and thriller while Weightlifting fairy is more lighthearted and slice of life. Both are enjoyable with solid acting from the cast

Both historical drama with good blend of lightness and serious/sombre scenes. Has a main girl and many visually pretty/handsome guys. Overall it gives the same vibe but different plot.

Both are short dramas with that good feeling of sweet romance. Both male otp look cold and sometimes rude. Both female although bright and good at what they do appears a little submissive to the guy.

Theme of solving ghost cases. Both male female leads have simbiotic relationship. In master's sun female lead uses her ghost seeing ability to be the male lead's radar. In Ghost the female lead is technically a ghost and helps the male lead to win against ghosts. Both male started off disliking the female lead to grudgingly accept their presence, then actively seeking them out when absent to forming a romantic relationship

Helmed by the same director. The focus is on a strong heroine who has brains and beauty but started off in a poor social position. Using her intelligence and cunning both heroines outwit their rivals and rise steadily within the palace to a position of power. They are realistic but never cruel.

Both these romcoms have a female lead whose different, quirky and bizzare. Oh Hae Young is perhaps more impulsive. Both females find themselves blurting amuzing embarassing things or situations. Both males are closed off and cold, seldom smile and even socially inept. Jo Se Ho in lucky romance is also bit nerdy and has an additional dimension in his character that really draws you in. Both become unwillingly drawn to the female lead and behave out of character.
Both dramas have poor first episode but gets better. The good acting and interactions compels you to follow their story.

The original Taiwanese version filmed a decade ago with Joe Cheng and Ariel Lin as the leads

The piano play invokes memories of Nodame. The male and female characters unknowingly allows them to grow and improve. The love of music and most important enjoying it is the gist of being happy.

Nodame drama is a bit more complicated as it involves the whole orchestra. Nevertheless both potrayed beautiful piano playing