My Sassy Girl (2001)

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.