The Mysterious Class

In Boseok Boys High School, the students of Grade 12 – Class 4 are trying to come into terms with the possibility of a ghost lurking in their homeroom after discovering that their class of 21 students was supposed to have only 20. A series of spooky events drove the students to suspect each other while trying to solve the mystery of their class' resident ghost, who might simply be posing as one of their classmates.