Petty Romance and P.S. Partner are good for movies, although they may not be as much of an emotional roller coaster ride as you want but it's still good.
Always and Coffee Prince I also agree would be good.
Something that fits your description perfectly would be Koizora, it's Japanese but it's probably exactly what you're looking for. Only 8 episodes, I would not recommend the movie because the drama is better.
I know you said Korean, but you should really consider watching these as well:
Taiwanese version: It Started With a Kiss/They Kiss Again
Japanese version: Itazura Na Kiss: Love in Tokyo/Itazura Na Kiss 2: Love in Okinawa
I wish I could recommend more Korean ones but I've had better luck outside of Korean shows when it comes to a story like what you're looking for.
