Flower Boy Next Door (emotionless FL, enthusiastic ML. He really has to conquer her)
Fool's Love (FL hardened by bitter life experiences, ML can't stop loving and caring for her)
I Do, I Do (FL is a bitchy business woman, ML is her younger employee)
I Hear Your Voice (FL is cold and calculating lawyer, the much younger ML remembers her better self from his youth)
Empress Ki (The most intense, interesting story imo about the lifelong bond between a strong, calculating FL and a softer, weaker ML)
I'm sure there are some Japanese series too on this subject, I just don't remember the titles :)