That Summer's Lie

First-year high school student Da Young is required to write about her summer vacation as an assignment. She chooses to write about her relationship and conflicts with her boyfriend, Byung Hoon, who is in the same grade. When she hands in the assignment, her homeroom teacher questions her about the shocking details, and she is forced to write a letter of apology, the contents of which make up the action of the film.
(Source: BIFF.kr)