Hi (again). 

Trying to find a drama/movie which show different personality of a character between a couple. 

1. His/Her personality towards His/Her couple is TOTALLY different than when He/She interact with other people.  I dont have anything in my mind for example now. 

2. or At first She's (He's) not in a friendly personality with her (his) couple, but once they couple, her (his) "real" (feeling comfortable towards close friends) personality shows up  since she (he) feel comfortable with her (his) couple.  - eg. Love O2O - the time when she bricks with her friend and go straight to Xiao Nai without saying anything, and he understand everything

See You in Time  Maybe not like what you're looking for exactly but: The second male lead here is so cold with others and when he is with the first female lead he become such a nice, kind man.

I'll try to watch this... Thats what I want... showing how different their personality when with their loves/ couple..... it just its SL not FL~