Traveling into the Supernatural World, the System Asked Me to Raise Ghosts for a Living

There is an unwritten rule in the supernatural world, that is, if someone knocks on the door late at night, do not ask or open the door, but find a secluded place to hide. But Yi Ze had just arrived and didn't know this rule yet. When he heard the knock on the door, he casually asked, "Who are you looking for?" The sound of opening the door suddenly stopped. He looked through the peephole and was confused. There was no one outside. Who was the one who knocked on the door just now? ....... System + Time Travel + Supernatural This novel and its characters are purely fictitious. Any similarity is purely coincidental and should not be imitated.