>>16120731Everything of the Underworld could have come from the Overworld. Demons and other residents could have once been humans, or their predecessors, who passed on and went to another realm. Mori even made the joke in her debut that she found Japanese Internet Rap because "It was dead." So maybe stuff gradually finds it way down there...but Mori also said Shrek and Adam Sandler movies were in her realm first because time there moves weird...brain hurt...
Regardless, where she comes from sounds really nice. When the time comes, I'm sure she will be a fitting ruler.