Do you mean like the male lead would end up with the second lead instead of the FL?

 cha delearth:

Do you mean like the male lead would end up with the second lead instead of the FL?

  1. No i guess it means he likes someone else but female lead likes him

There are many series that have some sort of a female antagonist that is competing with the FL for the love of the ML. A previous love that came back from overseas and wants to get  back together with the ML. Or the ML has strong lingering feelings for a woman that moved away. These series are too many to list :)

But for your description I think this series fits the best:

Goong    The crown prince loves another girl and proposed to her but got rejected, the FL is the secondary choice for the marriage.  

All these dramas fit your requirements (ML loves someone else in the beginning while the FL already loves him)

Dramas where the ML doesn't love the FL and no other girls either in the beginning. FL is chasing him to get his attention.