Before anything else: there's a fix in the second post of the thread. If you don't download that you'll get errors when talking to a certain NPC, and you will also not see many of the sex scenes in the game, as well as a number of voice clips and a few interactable objects. Why is this the case? Presumably, whoever ran the AI chainsaw through the game probably translated the names of the files in the json files.
With that out of the way, the game, which I can sum up as: Unfinished.
Not in a "they're still working on it" way, or a "everything's broken and you cant 'complete' it" way. There's technically an ending! Technically. More in a "everything here is good, but there's nowhere near enough of it to qualify as a finished project" way.
First off, what seems to bother a lot of the other reviewers is the CG; there's not a ton of it, and if you dont apply the patch (which I didnt, until after I finished the game) you'll see even less. What is in the game is pretty good, although it divides its available art further with some BDSM art, and a scat scene (which warns the player ahead of time, allowing them to skip it).
The game utilizes two fighting systems (more on one of them later), one of which is sex combat. This isn't as fleshed out as Karryn's Prison, Tales of Androgyny, or Lilith's Throne; you pick a position (which changes Kikka's picture), and then you use a separate command to penetrate with Gaggy (Kikka's master), while enemies take turns using 1-2 different attacks depending on the position. There's only two enemies with these CG's, and the game doesn't do anything to highlight them; in the aforementioned games there's typically dirty talk, animations, and/or descriptions of what's happening. In this game they mount Kikka, she plays a moan clip, and then they cum and disappear. It's not helped that these attacks also play out like...1.25x faster than they should? There isn't a lot of time spent lingering on them.
Outside of the porn, all the important characters (and a few NPC's) have drawn profiles which look good, and while the art is RPGMaker assets, they have edited the sprites to fit their profiles (and the edits don't stand out). They also use the assets fairly well, with most areas not feeling too empty or unimpressive. Special note to the goblin hideout, which does a decent job feeling lived-in with its assets, and implying that there's a community of goblins just offscreen. What little of game that is here is supported well.
Outside of sex, the gameplay is very basic; in the second combat system (in which you actually perform combat), you have several moves as well as a healing action. None of that matters. Kikka has one move that deals around five times more damage than all of her other moves, which she has available at the start, and hits everyone. The only encounters that do not get one-shot by this move are the two bosses (spoiler: the game has two bosses). They get two-shot instead. It's very obvious that real combat was not at all a focus for the game, because on top of that, there's no experience system or any other form of self-betterment, outside of getting money (there are 5 consumables in the game, and they give you all of them in ample amounts through the crates littered around the maps). Combat is primarily here to make the game feel more like a Game, because without these encounters, you'd just be bouncing between 5 locations.
What's outrageous is that even here, with a combat system so obligatory and unimpressive....there's signs of unfinished plans, just like the rest of the game. Gaggy can equip several weapons (Gaggy cannot fight in these encounters), and there's a consumable rock that deals 20 damage (presumably for Gaggy, as Kikka deals damage in the quadruple digits).
Sound design is....not really here. There's the stock RPGmaker music tracks, theres a couple of moans from Kikka, there's a character who does nothing but shows up in each town who has one line when talked to, nothing that's going to make you go "oh, that's hot" or "huh, good work!". You might think it's silly to critique a porn game on sound design, but it actually does contribute a lot; Karryn's Prison is made much sexier by the vast library of voiced lines (even if they like saying "dick milk" a bit too much), and Bounty Hunter Kyouka's absurdly long panting & moaning tracks make what's a pretty basic japanese porn game a bit more memorable.
And now the 'best' for last, the story. The tragedy here is that the plot as delivered is actually a lot more interesting than your standard porn game affair; it starts out very standard, with Kikka surrendering to the villain to protect her people, only for the villain to lie and kidnap them anyways. But that's where the game starts getting interesting...
Extremination Shrine Maiden Kikka actually features two protagonists, Kikka and Gaggy. Kikka is the typical overpowered super protagonist, and Gaggy is a stupid drunken goblin who's main trait is being obscenely lucky (this is actually pointed out in his stats). You play as both, usually together but at times separate. The conceit of the game is that Kikka normally could go straight up to the villain and kick their ass, but she's been given a slave brand which confines her to Gaggy's will. And Gaggy's will is usually "get drunk, steal shit". On paper it's a pretty amusing premise; the hero trying to find ways to go beat the bad guys while their partner pulls them on a leash (somewhat literally here) towards blackjack and hookers.
To add another wrinkle; when Gaggy gets drunk (on alcohol fermented in shrine maiden asses. Yep.) he passes out, then transforms into a goblin-ized form of Kikka (Clone? Personality Shard? Shadow Jutsu? The game doesn't draw that much attention to the quirks of it, and the translation work doesn't help. We'll get to that.). This Goblin-Kikka posesses her pre-capture personality, whereas her enslaved physical self is docile and subservient. Again, this could make for amusing writing; finding convoluted ways to knock Gaggy out, and struggling to manage two bodies at once.
I didn't intend to outright write a synopsis of the game's plot, but it's important to understand the potential of what the game could have to know why this sucks: there's one boss that you fight during the story, and they're not taken seriously as a threat (not in a comedic way, they're just not important) and are serving the real threats; you beat them once and they cowardly run away, then you beat them again later, and then the game ends. You backtrack between a few locations that are a couple feet from each other, fight the same person twice, and then the game is over. The game has to tell you that it's over, because it doesn't feel like an ending at all.
Like everything else, there needs to be more. This isn't really a 1.0 game, it's closer to either 0.45, or Shrine Maiden Kikka: Episode One. A lot of Japanese porn games are like this, but those games usually have the indignity of possessing worthless throwaway plots; Shrine Maiden Kikka wants you to be interested, and it does have some interesting ideas. It just doesn't do anything with them.
With everything on the developers' part finished, we can get to the elephant in the room; the MTL. Like all MTL's, it's fucking awful. It has all the dry chalk prose of an MTL job, but with all of the nonsense sputtering that MTL's do when the writing gets more flowery/obtuse/abstract. The person who ran the MTL did zero editing afterwards, which leads to all the hallmarks of an extra-bad MTL effort; half the NPC's in the game are called Kikka. Kikka's gender randomly fluctuates between He and She. The game inconsistently jumps between different terms for the same object (Kikka's source of power is an orb in her ass. This orb alternates between being called her Ovaries and her Testicles. Somehow it avoids Prostate, which would actually be the closest sex organ). All the classics. Seeing as the premise is the biggest positive in this game's favor, the bad translation really does it no favors.
As a whole, Extermination Shrine Maiden Kikka is not very good. But at the same time it makes me interested in the creator's future work, because they seem to have more creative ideas than most of the creators in this genre. It's much more interesting when a game is average via squandered potential than by just being short and boring.
So yeah, that's an obscene number of words written for an unimpressive porn game that I played for about an hour at 12 AM. Hope someone got a kick out of this.