Gyun Woo is a college student, more interested in picking up girls, drinking with his buddies and avoiding his nagging mother whenever possible. While riding the subway, a drunken girl then changes his fate forever. She's nearly unconscious on the train and vomits on an older guy. She then leans over to Gyun Woo and everybody assumes she is his girlfriend! Gyun Woo soon finds himself in a relationship he didn't ask for, but soon unable to forget this sassy girl.
In both, the FL sees ghosts constantly which has caused her to be reclusive, eccentric, and shut herself off from other people. At some point in the drama (all vs. one scene) the ML appears as a ghost but is not really dead, but the FL thinks he is dead at first. Both dramas have a very similar feel (Ghostderella is basically a condensed, shortened version).