49 Days
7th Grade Civil Servant
A Love to Kill
Arang and the Magistrate
Athena: Goddess of War
Bad Guy
Big
City Hunter
Cruel City
Gu Family Book
Haeundae Lovers
Hong Gil Dong
Iljimae
Innocent Man
Missing You
My Girlfriend is a Gumiho
Prosecutor Princess
Queen of Ambition
Rooftop Prince
Shark
Sungkyunkwan Scandal
The Bridal Mask
The Incarnation of Money
The Thousandth Man
Time Between Dog and Wolf
Vampire Prosecutor/2
Jesus Christ there isn't a single Korean drama where one of the main leads doesn't have a secret. These all have a somewhat secret identity, in some cases the other lead character knows about it from the beginning, in others it doesn't.
