Looking for dramas in which the lead has a secret identity that they hide from other people. Can be secret agent, or even someone hiding their wealth. Preferably Korean, but I'd definitely look at dramas from other countries. Thanks in advance!

Something like these: 

  • Healer
  • City Hunter
  • Joseon Gunman
  • Time Between Dog and Wolf
  • Bridal Mask

Rattling some off the top of my head that are good ones:

queen for 7 days
shark
cruel city
sorry I love you

love me if you dare (cdrama)

 JoanneSmith:

Rattling some off the top of my head that are good ones:

queen for 7 days
shark
cruel city
sorry I love you

love me if you dare (cdrama)

Queen for Seven Days I've heard of and have been wanting to watch, the other I'll definitely check out!

 Ashe:

Queen for Seven Days I've heard of and have been wanting to watch, the other I'll definitely check out!

there really are so many out there.     I'll go thru my completed list later and pick off some more.  

in addition:

  • Nirvana in Fire (China, historical) - hid his real name/identity for retribution
  • Money Flower (Korea, melodrama) - hid their real name/life for revenge
  • The Devil (Korea, thriller) - Hid their real name/life for revenge
  • Maou (Japan, thriller) - Japanese version of The Devil
  • The Disguiser (China, action) - a spy/secret Agent
  • Sparrow (China, action) - a secret agent for the communist part
  • Ouruburos (Japan, suspense) - hid their real identity for revenge
  • Man to Man (korea, action) - a spy/secret agent
  • Khun Chai Ronapee (Thailand, romance) - hid his higher status (Princelyness?) from the FL
  • Dr.Storks/Kounodori (japan, medical)- hid his cult followed piano master alter ego
  • Hwarang (korea, historical)- Male leads (2 leads) has royal blood
  • Pinocchio (korea, romcom) - hid his former life from his family
  • High society(korea, bad melo) - FL is a heiress
  • lovers in prague (Korea, romcom) - FL is the president daughter
  • Secret chaebol heir/heiress mini plot: Witch Romance, Dalja Spring, Golden time, ugly alert, 

✔️ Lookout

✔️ Guardian (Chinese) 

✔️ Mirror of the witch 

✔️ Shopping King Louie (has amnesia so doesn't remember  he's rich)

✔️ Ruler : Master of the Mask

✔️ High School king of savvy 

✔️ Your Honor

✔️ Switched (Japanese) 

✔️ Please Come Back Mister 

✔️ I AmNot a Robot 

✔️ Are You Human Too

✔️ Shine or Go Crazy 

✔️ Revolutionary Love 

✔️ She Was Pretty 

✔️ Strong Woman Do Bong Soon

✔️ Hello Monster 

✔️ Tunnel 

✔️ Hwarang

✔️ Switch 

✔️ Good Witch 

✔️ When We Were Young 

Genderbender ( girl pretends to be a boy)

✔️ Love in the Moonlight

✔️ You're Beautiful

✔️ Coffee Prince 

✔️ To the Beautiful You 

✔️ Sungkyunkwan Scandal 

  • Cheongdamdong alice
  • Iljimae
  • Hwarang
  • Ruler master of the mask
  • Yamaneko
  • Lookout
  • Suna no utsuwa

In addition to the ones already mentioned:

  • Mask | FL takes over the identity of a rich heiress who looked like her.
  • Are you Human too? | ML is an android created to look like his creator's son.
  • Moon Lovers: Scarlet Heart Ryeo | FL is from the future.
  • You Who Came From Another Star | ML is an alien.
  • Black | ML is a grim reaper.
  • Oh my Ghostess | 2FL is a ghost (I'm adding this since you could argue she's actually the FL since she spends more time "on screen" than the other girl).
  • Strong Woman Do Bong Soon | FL has super strength which she keeps a secret from everyone.