This is one of those things that I'm not sure I should be it to having read. It is, after all, illegal in my country.
Let's clear up any ambiguity: This is porn. Lolicon guro, in fact. If that doesn't tickle your fancy, you shouldn't read it. Yes, there is a plot - but the porn : plot ratio is tipped quite strongly to the porn.
I didn't enjoy it much. Intestines are not sexy.
If the porn : plot ratio had tipped the other way, I imagine I would have liked it a lot. The characters and plot are actually pretty good. Around a quarter of the way into volume 4 it leaves the porn and we get badass demons and tragedy. Maybe even depth?
But, well ... I've read porn for the plot before and it worked well. It just didn't this time. Even though the good elements are present in the earlier volumes as well, they're overshadowed by the porn. The earlier volumes are getting better in retrospect, but I at the time of reading thinking that I'd definitely not recommend this to anyone who isn't in it for the porn - so there we are.
If it had all been like volume 4, it would be getting an 8 or 9. As-is, I guess I'll leave it unrated. I'm sure it's good for what it is, I just don't especially like what it is.
(And don't take this as a squeamish I-hate-gore thing. Among my top-rated series are Narutaru and Bradherley's Coach. It's the role of the gore that doesn't do it for me here)