Try Sleeping in a Haunted House, There Is a Person Hidden in the Mirror

In order to investigate the truth about my sister's "suicide", I annoyed my boss and was expelled from the police force; in order to survive, I had to accept the job of a sleep tester in a haunted house. In the mirror in the haunted house, there was another me trying to replace the real me. I was forced to be involved in one serial murder case after another, risking my life again and again to rescue the deceased who was trapped by my own obsession...