In both dramas the partners of killed people fall in love with the person who they know/believe to have killed their old love. It becomes a story of much sadness about how they supposedly betray their old loves but also how they attempt to move on from tragedy.
Male lead killed female lead's husband.
They fall in love without knowing who each other are (in that regard).
Annoying second male lead friendzoned by female lead, won't leave her alone.
Female lead is close with former in laws.
