Choi Hyun-uk, a third-year student, receives an A on his math exam and tells his friends that he made this wish through a strange app. Kim Gon-u also downloads the app and jokingly asks his girlfriend to cancel her training session the next day. However, when Hyun-uk, unable to resist an invisible force, slits his own throat in front of the entire class, the students realize that Gon-u is in grave danger. The app cannot be deleted, and a countdown timer appears on the screen after the wish is granted.