want to watch romance where the guy is older than the girl and the girl calls the guy oppa (prefferred)
doesn't need to be huge age gap can also be a few years
Prime Minister and I...... I don't think she called him oppa tho xD 
You Who Came from the Stars
My amazing boyfriend
Dramas about vampires like Blood
 Scholar Who Walks the Night
Goblin but she doesn't call him Oppa ever. Well worth it though!
Marriage Contract... but she doesn't call him oppa 
I don't remember if she calls him oppa, but in "When A Man's in Love" the guy is somewhat older since they meet when the girl is a student and he is a gangster.
Hello Schoolgirl is pretty good but it's a movie not a drama.
i think Hello, Mr. Right will be in this list