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You get the same feeling from both dramas, even in some scenes.
Same actress as female lead
Male lead is also a character in the drama
Both male leads are medics.

Written by the same writer. Similar ambiance. Thrilling watch!

both dramas feature an old, historic and conservative family that has to face a lively (future) daughter in law.
While the FL has to adapt to her new family, the family is changing because of her.
Similar is also the drama sweet 18 (https://mydramalist.com/294-sweet-18)

This drama is basically about biotechnology and superhuman abilities. Bottom line - human experimentation.

Friendship, relationship and family. OXYGEN THE SERIES and TONHON CHONLATEE are two of the most popular Thai Bl Series.

Similarities is that both series have spy that help police investigate illegal activities. in YLM the spy is ML and the storyline is quite serious and heavy while in KWHNPSL the spy is FL and story is quite light and a lot of funny moment.

Vastly different in terms of plotline and subplot lines but the ML in both the dramas are young and have a lot to learn- they fall for someone older and look up to them and want to take care of them. ML's in both listen patiently to what the FL has to say and thus their character develops throughout the show.

Both series involved ML becoming a spy to investigate illegal activities and corruption. The FL family are closely link to case the ML investigated

The similarities of both show is the betrayal and a lots of screaming involve where the FL is cheated by their lover. There is rival between the sisters in both series

The story revolve old story of thai and both show have the main FL character very strong even during ancient times which is rare.

Both show have ML that very protective towards FL and there is a family fight in both series. However NRNKF the main couple only see each other after grow up while YLM the main coiple always be there for each others from young until grow up.

Both involved mafia story of the chinese family and the fight of the gang to become the most powerful mafia. There is love story in both series

Mafia stories revolved around gang fight and people involve with the gang. Also both have love stories involved

It's the same producer (Na Young-Seok). Basically, the same premise of having celebrities work but the difference is one is about a cafe and one is with a boarding house. Both are very relaxing to watch!

They give off the same atmosphere
Wintery themes, slow burning romance
Of course A Piece of Your Mind is more calm and toned down.