Bad Lover.

Joo-young, a high school student, likes her neighbor, Surim. Joo-young sees Surim with her lover, Sung-joon, and feels jealous. Later, Joo-young gets asked out by Eun-ho, a student from school, and tells Surim about it. She feels frustrated by Surim's indifference. One day, Joo-young happens to see Sung-joon with another woman, cheating on Surim.