Tentatively, this will be a New Orthodox mystery, or a setting-based mystery.
I might add elements of infinite-flow fiction or monsters, but that's undecided.
In other words, it's a story where the supernatural elements are established up front, and everyone solves the mystery using the setting and logic.
I might also write a hybrid mystery or an everyday-life mystery. In short, it's going to be a mystery novel.
The start date is undecided. I need to build up a few cases first.
Theme: Think hard