Inside the Cave of Obscenity


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A world where the [Demon King] was defeated by a [Hero] that came from another world. People carelessly forgot about their fear of the [Demon King] and of monsters, living in peace.

In a forgotten and run-down cave in the mountains, a new monster that should not have been born was given birth.

The monster’s name was the [Black Ooze]. It was nothing exceptional other than its black color, an ordinary slime.

However, this slime had the special characteristic of being able to take the abilities of the living things it swallowed. It preyed on an insect that had paralytic poison, as well as other animals. Following that, it attacked a human, obtaining his knowledge and [Desire].

Before long, the monster established its target as the female mage that came to explore the cave.

This world still wasn’t aware.

[A Monster Was Born]…

Associated Names
One entry per line
Inbi na Doukutsu no Sono Oku de
Related Series
Happy Peach (3)
Bishoujo wo Jouzu ni Nikubenki ni Suru Houhou (2)
Ero Gacha (1)
Adventurer Lindy’s Calamity (1)
Maou no Hajimekata (1)
X-ray Is More Than I Thought (1)
Recommendation Lists
  1. to watch
  2. JP Light Novels and their weird names! 2
  3. novels for 'plot'
  4. Novels That Suit My Taste
  5. R-18 (no yaoi or smut)

Latest Release

Date Group Release
07/29/20 Centinni v3c1 part16
07/28/20 Centinni v3c1 part15
07/28/20 Centinni v3c1 part14
07/11/20 Centinni v3c1 part13
06/30/20 Centinni v3c1 part12
06/23/20 Centinni v3c1 part11
06/18/20 Centinni v3c1 part10
06/08/20 Centinni v3c1 part9
06/06/20 Centinni v3c1 part8
06/02/20 Centinni v3c1 part7
11/10/18 Ziru’s Musings v3c1 part6
06/07/18 Ziru’s Musings v3c1 part5
03/17/18 Ziru’s Musings v3c1 part4
02/26/18 Ziru’s Musings v3c1 part3
02/02/18 Ziru’s Musings v3c1 part2
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21 Reviews sorted by

Ziru Asteri
Ziru Asteri rated it
August 22, 2016
Status: v3
Before reading this series, I believe that it is important to realize that it heavily includes the following elements: r*pe, tentacles, mind break. These are not for the faint of heart, and if you are someone that does not like those themes, this series will absolutely not suit your interests. I implore you, please do not go into this expecting something that this novel is not. It will only serve to sour your mood!

That said---

If you are fine with those themes, however, you'll find the flow of the writing and... more>> character progression---as well as their sweet, sweet degeneration---to be better than most other translated ero novels in our community. Written in a mix between third-person view and first-person character thoughts, this series centers around a monster that should not exist---the [Black Ooze]. In a world that has firmly settled into its post-demon king era, no one suspects that something like a monster could exist in such an out-of-the-way abandoned mine. If you are intrigued for what happens after that, I wholly recommend giving this series a shot.

Also, if you love breasts, you'll love this.


Our main character, the black ooze, doesn't particularly act as one---at least, in this first novel---so much as a plot device of honeybadger proportions. From what we see in this first volume, its intelligence is improving over time as it absorbs more and more of its prey. We didn't get to peer too much into its head this time, but perhaps we will in the volumes to come?

99 Likes · Like Permalink | Report
October 3, 2016
Status: v2c1
If you like novels with happy end (-ings), this will be your source of juicy joy. 69/5 stars - it's one of the better ero novels out there, naturally, only in comparance to the genre in general and if you're fan of c*ck magic.

Believe it or not, but we have some actual story going on here, with monster (character) development and plausible monster ecology story-telling.
27 Likes · Like Permalink | Report
kenneth223 rated it
August 23, 2016
Status: v1c2
Trust me, not for the good of the heart. You will feel weird inside and even your PP will feel weird when you're reading it... must fap more!

An Intellectual slime; Tentacle r*pe with possible impregnation. Basically, just tentacle r*pe play.


PS. You will definitely 'fall'.
25 Likes · Like Permalink | Report
0000000 rated it
February 5, 2017
Status: v2c2 part6
Giving it a full 5* to show just how messed up I am lol. Jokes aside, there are actually character developments and stuff, weird because we are having such developments at this early stage, most novels at this stage are either donkan MCs s*upidity, kill kill kill, slice of never changing life, etc etc. Also, giving it a 5* for loving how the MC likes to screw with the victims, male and female. For female, it's r*pe until they mind break, which seems plausible yet I am doubtful... For male,... more>> it is killing them slowly while making them watch the female gets r*ped, makes it more messed up as the female, who is being r*ped, is watching the male slowly dying. Like 2 perspectives, male -> female: look how nice of me to let you have a grand view before dying. female -> male: look how nice of me to let you live while the other guy is dying painfully.

Really hope that there is actually an artist out there working on this piece here. <<less
19 Likes · Like Permalink | Report
San-Kyu rated it
March 26, 2017
Status: v2c3 part2
The premise is interesting enough to warrant reading just for it. You have a protagonist that isn't human and it isn't just about their race or body. Its a slime that thinks in a very logical and curious manner, with absolutely little in the way of morals that other R-18 protagonists usually exhibits. Even the rapist protagonists aren't driven like the slime here, pretty much all it does is for sustenance, learning, growth, rather than for its own pleasure. The fact that it dabbles in more deviant themes such as... more>> tentacles, slime, drugs, and mind break is something to consider. The whole thing is written a bit like a horror story with the protag as the monster/villain. Updates are very slow however so be warned that the novel continues for quite a bit but the translator isn't focusing on this so that kinda sucks. <<less
11 Likes · Like Permalink | Report
September 9, 2016
Status: v1c2
This other reviewer... nothing about the name, description, or tags is misleading, and he wants to be outraged and rate it 1 Star when the story is exactly as presented. Seems more like he's in denial about his own tastes. Also lol, "garage".

Anyway, this is some fairly hardcore smut, but it feels like the author is setting it up to be a genuine horror story too. Like a catastrophe that descends upon the kingdom and results in widespread despair. In other words, closer to a Lovecraft monstrosity than a typical... more>> ecchi anime. It doesn't shy away from gore either, the story is perfectly willing to describe creatures (and people) being killed, smothered, torn apart, or consumed.

With only two chapters so far, it's hard to say, but the writing and translation quality are fairly top notch for now. We'll see how it goes. <<less
10 Likes · Like Permalink | Report
kane2929 rated it
April 3, 2019
Status: v3c1 part6
this is... AMAZING!.. my fap count is in the double digits for this.

cave of obscenity is another novel that proves that SLIME protagonists are really the best, followed by a certain spider.

i wanna read more chapters but the releases are so slow and so... please!! spread this around, share this to your otaku/hentai friends and make this novel popular enough so that the translators will place more priority on Inside the Cave of Obscenity. Do this to make fellow men happy.
9 Likes · Like Permalink | Report
fearthedeep rated it
September 17, 2017
Status: v2c5
Truly a masterpiece, I love "constant orgasms" and "forced orgasms" work and this is truly a tier above in those categories. (ಠ ͜つಠ)

If you're looking to fap and also be intreguied by some plot, this is for you. It's basically p*rn with a good plot! XD

7 Likes · Like Permalink | Report
mmem rated it
August 23, 2016
Status: v1c2
Too soon to tell but I like the writing. Wish the author was kinder when describing women.

Seems like there could be an interesting plot but the story may end up just being about girls being r*ped and mind broke by a slime. Currently looking forward to more chapters.
5 Likes · Like Permalink | Report
NovelHamster rated it
June 2, 2021
Status: v3

The protagonist is a monster slime that can't even communicate. It keeps on tentacle raping all the women it comes in contact with. The women magically fall in love with it after experiencing orgasms. The human females also somehow bear slime children.

That's basically the whole story... I was expecting the slime to be able to transform and be intelligent, but that was a disappointment.

I don't have a tentacle r*pe fetish, so I can only treat this as a comedy. Even as a comedy, the story is quite repetitive and predictable.... more>> You won't be able to read through it if you aren't a tentacle enthusiast. <<less
3 Likes · Like Permalink | Report
berdanka rated it
July 22, 2019
Status: v2 illustrations
This story is really nice and balanced for an adult novel about monster raping innocent girls. This is not isekai and the monster is really not a human. It just likes to "hunt" girls for a specific reason. It is merciless to men but it doesn't kill women. Though women not treated like humans, they fed, protected, and heavily loved.

Multi-pow storytelling makes things wonderful. Every pray have some depth and backstory. And women are still significant even after being r*ped. They are broken but still keep their individuality. It's important... more>> because I hate hypnosis and complete mindbrake.

Overall the balance is good. It's not a brainless s*x script like it usually happens with short r18 novels. Also, the illustrations are great.

If you searching for a lewd novel with some proper story and you don't care about tentacles r*pe, then this one is exactly what you need. Though it's a shame that it isn't fully translated yet. <<less
3 Likes · Like Permalink | Report
Adesina66595 rated it
December 21, 2020
Status: --
if you read the negative review of this story youed see that the people who write them either didn't read the summary are dumb or are just SIMPs that can't Handel this story this story is great and is the one of the best if not the best. R-18 novel you can find on novel updates the MC isn't a horny dog like most MC's you find In other r-18. Novels the author writes the story in a way that makes it both a r-18 and horror story... more>> at the same time the MC is a a slime that wants to survive and grow he's not a reincarnat but he gains knowledge after find out how to impregnate female s he start to create of spring and you know were it goes from there I'm not good at making reviews but I advise you to read this is going to be healthy and pleasent for both you and your little brother you might even increase your cultivation base (meaming grow in size) <<less
2 Likes · Like Permalink | Report
SisConEcho rated it
October 19, 2018
Status: v3c1
I came here coz Tensei Shitara Slime Datta Ken was a bit lacking in "Slime" and character growth.
This Slime here faces more meaningful challenges and side characters are a bit more developed as far as ero goes.

I'm rating it a 3/5 as word choices and phrases get pretty repetitive, and the plot advances very slow.
I may be too harsh as I see great potential with this writer in storytelling but am left feeling even more empty due to the want for more story and development.
2 Likes · Like Permalink | Report
poppitypop rated it
August 18, 2021
Status: v2c3
The slime protagonist has potential, but it's difficult to get identify with. Telling the story from other people's perspectives, predominantly, gives off a netorare feel as opposed to a netori feel. I can put up with netori, but NTR is just plain unpleasant to me.

Technically, it's netori since the slime is the protagonist. However, if you need your protagonist to be somewhat human to identify with them, then you might experience the story as NTR too. If you're into NTR, this could be a novel for you. Otherwise,... more>> skip it. It'd have been better if the story was written in a way that'd allow you, as the reader, to identify as the slime. <<less
1 Likes · Like Permalink | Report
HentMas rated it
October 11, 2020
Status: v2c3 part3
I was waiting for something to move forward but... it's just r*pe after r*pe after r*pe after r*pe after...

you get the deal...

If you want to read something with the same vibe but actual story, go read "Maou no Hajimekata" because that one is much more competent even if filled with s*x and all the perverse things this one haves, it haves an actual plot and set up and pay off and... it's a real story.

This one isn't... sexy, isn't... exiting, isn't... anything other than a jumble of things that... more>> "happen".

It's just... perverse without rime or reason.

V3 it's the exact same thing...

I don't mind works with NTR or Mindbreak or whatever else, but this one isn't interesting to me, I want to see some character progression, not just... a thing that f*cks... <<less
1 Likes · Like Permalink | Report
Nightfkhawk rated it
August 18, 2020
Status: v3c1 part10
Honestly, the concept is very interesting, and it is somewhat well done but... It became boring. Ever since the start of v3c1 it feels like there is almost no progress. I find myself skipping multiple paragraphs for they have absolute no meaning.

However, I will keep going, as there is some development every once in a while...
1 Likes · Like Permalink | Report
wolzimon rated it
October 22, 2018
Status: --
Much like everyone who said it was good, I would say the same.

Only that the word of choices seems lacking, but perhaps, that wasn't the author fault. Just probably translators unable to think a better way describing the situation in "English".

I am giving it Four because of translation. In case where the translator has become better, Let's make that as Five.
1 Likes · Like Permalink | Report
July 4, 2018
Status: v3c1 part5
80% slime tentacle r*pe and mind break, described in great detail. Mashed into the rest are decent character development (for the genre, at least), good world building (given the space it's got), some story development and the underlying possibility of a deeper plot unraveling at some point in the future.
1 Likes · Like Permalink | Report
JokerXY rated it
March 18, 2018
Status: --
Prety good read, it balances the gap material with the plot pretty well. Honestly though I can only see this going one of three ways: either the slime grows intelligence and stops mindlessly reproducing let’s be real not happening anytime soon. Or it kills and r*pes everything and destroys the world, or lastly the nations rise up and kill the slime whil becoming more vigilant to new threats being born
1 Likes · Like Permalink | Report
Patchi_ rated it
March 26, 2021
Status: v3c1 part6
Very good. That's your review.

IMPORTANT: v3c6 is a last chapter translated.

At the moment of writing this review I decided to start learning Japanese just to read all the other volumes. There is 11 volumes all 500 yen each. That's how much I like this novel.
0 Likes · Like Permalink | Report
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