The main story is interesting enough (though 2 other shorts are included. I'll go over those later) and develops at a decent pace. Without going into details, there are questions that you will have that the story will seemingly answer, only to bring about more questions. However, through a twist toward the end, all these revelations are reversed, closing up the new questions and reopening the new ones.
This does close up a plot hole that would otherwise have remained had the final twist not occurred, but it seemed rather sudden and left me somewhat confused as the why so much effort was put into the plot development, only for it to be swept away in the last few pages.
I've taken a liking to horror media lately, getting into movies and books. Now I don't know how popular slasher films are over in Japan, but as a westerner, I've had quite a bit of exposure with the popularity of stuff such as Friday the 13th and Halloween, etc. As I stated before, Ibitsu is at its core a slasher story. Unfortunately, slashers have very well-known set-ups and tropes. As a result, much of Ibitsu's set-ups into what would be shocks and surprises, are instead very predictable and lose much of their effect. Without going into detail, you'll see what I mean (even just by comparing to some generic slasher films). However, some of the smaller details as well as general atmosphere manage to keep up an aura of general suspense, preventing this manga from falling flat in the scares department.
The art is very clean and looks quite nice and the backgrounds and settings are of decent quality too. The characters are distinguishable from one another and the design for the antagonist is pulled off well to create an unsettling character. So this was pretty good.
Due to the short length of the series (only 2 volumes) not much character development can occur, but the characters are fleshed out enough that none of them seem particularly wooden, although most fit into certain basic archetypes (such as the friendly and caring younger sister and the goofy and relaxed friend).
Onto the two bundled shorts: as they depart from Ibitsu's story, they also leave the slasher style behind. This allows freedom from the predictability of the well-known slasher set-ups and so have more potential to scare, or in the case of the second one, just creep you out. The same good quality of art is present in both, and story-wise both are interesting enough (the first being a typical venture into an abandoned building that and the second is basically Bakuman: the Misery edition). They're alright, but nothing special.
CONCLUSION/TL;DR
For me, the biggest issue i had was the predictability of so many of the situations presented in Ibitsu. If you haven't had much exposure to common horror tropes (and I find this unlikely if you've gown up watching Western TV. Even non-horror media will borrow some of these ideas), then it will be a better experience for you. But for me it borrowed too heavily on very well known and generic horror situations and was only saved by a creepiness created by the overall menace in the atmosphere and some nice art. Not a must read, but its decent enough, even if you can see most of it coming.
