Junji Ito is a pretty wonderful guy, but I do find his stuff kind of dry after a while. I got pretty bored of Tomie. However, he does do horror pretty well -- he isn't presenting you with OH SCAAAARY things, you know, the cheap shitty jump scares.
If you want to know how to do horror well, find some good short fiction. I feel like those are often the best you can find. But let's be honest, EA Poe is boring as fuck and classic horror doesn't translate well anymore. Lovecraft does do some good stuff, but I feel like his short, elder god-free material doesn't go as far as it should. Most Dangerous Game is pretty nice, though likely not the horror you're looking for (read it anyway).
More up your alley for inspiration ... ah, of course.
I Have No Mouth and I Must Scream. Also play the game if you can find it, good stuff.
Oh, found you this.
http://www.classichorrorstories.com/stories/stories.html Read. Some of them are pretty good -- lots of Lovecraft works on there, classics like The Monkey's Paw, Minister's Black Veil, etc.
Find the Yellow Wallpaper if you're going the madness route, I think.
Maybe try an excerpt of
House of Leaves.
The thing is, horror is not in gore or flash fear. You don't need to have huge spiders or thousands of dead people everywhere to scare someone -- it kind of cheeses it up and dulls the end horror. I find the most effective horror is the lingering kind. The kind that takes something average and makes it scary, or that makes you afraid of something that
could be there.
You know when you look at a picture of a long dark hall and expect something horrifying to show up, only realizing it's not a .gif
after you've terrified yourself?
Gotta say though, the mental hospital thing is pretty tired. The anything hospital thing really.
Lemme see if I can find some good horror manga.
