There is this movie called Love Exposure, I loved it but honestly it really depends on the person you might think it's disturbing Also for the challenge a lot of people watched this: KANO and The Bride of Rip Van Winkle, that's all I know
Does it have to be Korean or Japanese? Because the Chinese epic Red Cliff is around four hours, I think. It's actually split into two parts because of the length, but it might count? Anyway, it's really good!