The Villain Who I Love(2017)

One day, high school freshman Minzy finds a photo of herself changing clothes in the school locker room. Class leader Hyejin, who is not close to minzy, points out that the new teacher is the suspect to her. Minzy and Hyejin collect evidences to prove that the teacher takes pictures of high school girls secretly. When Minzy and Hyejin report the teacher's behavior to another teacher, Minzy realizes something unexpected.