One Day (2014)

A high school student, Ho-jin (17 years old), is shocked when her boyfriend, Young-ho (32 years old) who is a teacher at her high school, suddenly breaks up with her. Yong-jin (17 years old ) who has a crush on Ho-jin, always stays near her and waits for her call. Chan-soo (17 years old) likes Yong-jin and tries to win his affection. Ms. Park, a gym teacher, calls on the heart-broken Ho-jin for afterschool dance practice. Ho-jin lies to Young-ho to avoid the break-up. However, Young-ho is gone without a trace afterschool, and Ho-jin finds the body of Ms. Park who has killed herself. On the way home, she sees a puddle, filled with rainbow color grease.