…’Who’s there?!’ he asked nervously, only to turn around and find a man stripping off his clothes and pointing his bare buttocks at the flabbergasted traveler. A huge glittering eye then opened up where the strange man’s anus should have been…
https://en.wikipedia.org/wiki/Shirime
How terrified would you be if you encountered this ghost? You’d have just been forced to deal with the fact that ghosts are real. That’s already got to be above your previous high water mark for fear. Then the ghost starts taking off its clothes, ratcheting up the level of unexpected. I would argue in a situation like this that can only produce greater fear. Now you know ghosts are real, but apparently very different than fiction prepared you for.
Then it turns around, drops to all four–and excuse the language but there’s little better way to say it–slowly parts its cheeks to expose its butthole. You were probably still trying to figure out ghost clothes (or just ghosts really), but now you are having to brace to see a ghost’s butthole. What’s back there?! You know it’s not going to be good. And what is this ghost doing anyway? Where does this go from here?! Again, can’t be good! But whatever you did in fact prepare for, I do not imagine it will have been a terrifying eye. Moving. Blinking. Scanning your body. I think this is about the worst that ghosts can get.