She's helping a guy (maybe the second male lead) cheat on their spouse. Either she's unaware that he's got a spouse or does and doesn't care. Eventually she falls for the male lead and the other guy tries to keep her by his side. 

  • Divorce lawyers (Cdrama) - loved this drama, i wish it had better subs. The 2 leads had so much chemistry and the FL is not some weak simpering girl. 
  • Bad Love (Kdrama) - watched this, but not really the best drama out there
  • Sealed with a Kiss (Cdrama) - this one always gets bumped down by other dramas in my watch list, so I never had the time to watch this
  • Perfect crime (Jdrama) - havent watched this, but clips i saw points that thisnis what you are looking for
  •  Mistresses (Kdrama) - havent really seen this, so i am not sure if this fits what you are looking for, though I feel like it does

Ubai Ai,  Natsu

Mistresses : Onnatachi no Himitsu