Watch Bad Sister for Free: How to Stream the Movie Online at 123Movies. . Professional astrologer Huang Ershan lives her life by the rules of the stars. When she learns that her brother is in Korea and is about to marry his astrology incompatible fiancée, she decides to fly straight to Busan to try and cancel the wedding. On the flight there, she meets the fiancée's father, and together they try to break up the marriage.