It could start by having a person enter your house. He says he's the cop and he's there to investigate, but slowly you have the realisation - he's fakeclaiming and he's here to kill you!

If you're trying to write something in the realm of horror, you could write about Chitose.

Talk about how indoctrination of impressionable teens through cultural trends shape society

Do something with the cultists, that would be creepy but awesome. Like, total paranoia fuel where no one is dying or anything, but people are slowly being turned into something else, and there's no way to tell who's converted or not. That would be a cool prompt.