A man is being haunted by a ghost, since exorcisms did not work they want Kogorou to solve the case. The clue is a card that says the fifth ghost will kill them unless they repent their sins. Since the time that card was sent, the master installed a door that needs a pin code and fingerprint scan to access the top floor. The master, lady, and the installer of the door are friends who are hiding a secret about the sin.
