I remember a scene in which a guy and a girl were lying down together and he descovered she had some scars (on her arms I think but dunno) and he got really angry (wanting to take revenge for her - I guess the scars were not a result of accident but rather deliberately caused by someone) and the point is I don't think they ended up together. so possibly he was just a second male lead here. to sum up: due to circumstances they were saying somewhere together for the night and that's when as they were lying in the dark he saw her scars. the genre of kdrama was probably romance I assume. I know it's probably not enough information to identify the drama but please if anything comes to mind let me know.