Every time you hear the word horror near anime or manga, it's closely followed by someone ranting about how great Junju Ito is. If this is the calibre of his work then I REALLY don't know where that's coming from.
The short horror stories range from the outright weird like an invasion of giant balloon heads that want to hang people to the utterly mundane, by which I mean 10 minutes straight of "this guys brother is irritating" with absolutely zero plot nor payoff.
The writing is inconsistent. In one episode the explanation for the event would be summarised by a shrug, because there was no rhyme nor reason to them, and the next you'll have a character halt the story for some painfully stilted exposition to explain everything they've ever done and how that relates to, at best, a mildly creepy plot.
The only way most of this even qualifies as horror is if you'd faint in terror because someone said the word "ghost" or vomit at something most would look at and go "oh, that's a bit gross." There's such little atmosphere, so little build up or tension, and even less payoff nine times out of ten.