The high school senior girls discovered a 'Ghost Hide and Seek' tape recorded by their seniors in the broadcasting club. Through the tape, the girls learned about a rumor that if they win in the ghost hide and seek game on the upcoming school anniversary, they can receive a perfect score on the college entrance exam. The girls decided to recruit Min-joo, a second year student from the religious club, as a mercenary and made a decision to participate together in the ghost hide and seek.