Do You Believe Humans Are Born Evil?

Can one put their faith in the existence of malevolent entities? Chae Seon-ho, leading a modest yet upright life, finds himself troubled by a vial of semen that has been sitting on his shelf for months. With a surge in the frequency of malicious pranks, Seon-ho and his closest friend Lee Yu-geon decide to keep watch in front of the cabinet throughout the night to catch the culprit. While trying to shake off drowsiness in the bathroom, Seon-ho experiences a disconcerting sensation in his lower body.