This episode is based on a popular Urban Legend that originates in both Japan and Korea, known as the "Elevator Game". It opens at a crime scene where officers are watching footage of a young man in the elevator who for seemingly no reason grabs his ears in pain. The man's body is severely decayed, despite him dying only the night before. The leading officer after hearing about the "elevator game" that the man had participated in, decides to try it himself. (Source: Sxngari at Mydramalist)