It's a horror film. This is the scariest film I've ever seen, giving me chills again and again. And it accomplishes this with relatively simple materials, such as a black cat, a black sort of mist, a little ghostly looking boy, fear as people realize what they're up against, bodies being found, the lack of any safe refuge. I'm reminded of how "The Shining" did this.
This may well be a neo-noir. It has a structure of segments and time that does this, and the ways in which the supernatural evil spreads from its source outwards to other locations do this too. There are gradual and increasingly explicit and horrifying revelations, as good and well-meaning people succumb. Definitely a pessimistic take.