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.

Kang Eun-kyung, who has come for her teaching practicum, encounters members of the Black Sky black magic club, who are ranked first in the national mock exams. She discovers that there is a witch behind the girls. To retrieve the souls that the witch has taken, she opens the door to the world of darkness.