Also just another minor suggestion of mine, but I feel like the use of elder god is kind of forced.

specifically the spiral god, I've read the manga Uzumaki and always feel like it's more of a cosmic event or a curse instead of just some sleeping god doing bad things, and it takes away a bit of the horror by personifying it a bit.

also by not limiting your mystery to elder god, it opens up more creative space and give this game a more distinct identity instead of Arkham horror/Eldritch horror clone, it's fine if you want to make a digitalized version of those two games, but in order to focus more on the Junji Ito aspect I feel you need a wider selection instead of different elder gods/bad guys.

of course others might feel differently and that a personified god is more terrifying than a cosmic event/curse/earthquake, so take my suggestion with a grain of salt.