Played on 1.0.8 with the patch.
Another title to throw in the corruption/ntr bin, but my lord is the heroine, Rain, unbelievably beautiful!! As much as I have complaints about the game that I will detail below, just play this game to enjoy the art to the fullest!
---Story & Characters---
The main story is a boring and uninteresting fantasy rpg romp - kick the evil and not-very threatening demon to the curve and be a victim of sexual assault along the way. The demon is transmitting horny waves to the entire city which is distracting everyone enough for them to ignore a giant demon invasion I think? Whatever plan the antagonist was trying to cook doing some dungeon crawling and destroying his magic crystals is enough to thwart everything. Yawn.
While this game is labelled as NTR and corruption, there's very little of either going on here. The heroine's love interest is a million miles away and there is zero build up of him finding out what she's been doing or even feelings of guilt on the heroine's side if she puts herself in certain scenarios that the whole angle might as well not exist. Likewise with the corruption, Rain never goes through a distinct progression of committing to more hardcore actions - it all blends together between shoddy justifications and being helpless against the horny waves and needing something from the other party, usually plot progression. There are no hard story beats of her turning into a cockslut, it's more like she is already one at the start but the game mechanics just put a buffer between the softer and harder stuff.
All this to say that maybe the chat gpt machine translation, although it spits out acceptable and understandable english, fails in the fine details of the text it translated. I won't knock the story too hard because ultimately what I've read has an unknown accuracy to what the author intended. But like I said, the translation is perfectly acceptable to get through the game and enjoy it without hiccups like a line of garbled garble.
One character that stands out though is Buster, an adversary that wants Rain at all costs and also is similar to her lover in appearance to boot. If you want to get the most out of the story, definitely accept his conditions to enjoy the best part of the story. Hell, even if you decline he ends up having some pretty cool dialogue at the end of the game.
To get all the scenes you unfortunately have to grind various sexual actions to max the level of Rain's desire, which is serious tedium. Because seeing the same cgs and animations just destroys the fun and joy of it all, consider a full save. There are points in the story where Rain must choose to give into desire or stick to reason, and the decision is left up to a bouncing meter and both sides constantly vie for room. With high desire, it's mechanically difficult to choose the "reason" and avoid sex scenes which is worth mentioning. Desire slowly builds up every day, so while there is no strict timeline you may want to manage how deep your desire goes.
---Combat---
Nightmare Knight also features bog standard combat - at this point it's not really a rpg hentai game if there is no destructible clothing, defeat scenes, and in-battle molestation. The game handles these all very well: defense lowers when more of Rain's hard-to-hold-onto clothing disappears, which actually makes enemy hits fairly damaging. If Rain gets held down by the monsters and she has no TP to immediately escape, it can lead to consequences down the line. Escaping by itself can be challenging as hitting the timing on the sliding bar is precise. However, there is a hard cap as to what a group of monsters will do to Rain in battle so they lose their luster after a while - there's pretty much no incentive to continue to be molested indefinitely - after 3 or 4 turns you have seen all you can see.
Something I haven't seen before is a two-state climax bar; typically the horny bar hits full and the heroine climaxes, but in this game it takes two of these bars filled to see Rain climax. With this system Rain has a dedicated state where she is more open to harassment, and her defense in battle is lowered. Climaxing in battle puts you out for five whole turns, and filling the second bar from a street molester leads to some funny sequence breaking in terms of corruption. Overall this is a neat idea as it opens up more time to enjoy some more lewd voice acting in battle.
The combat itself is unfortunately very easy. When you see the sparse skill tree and what some of them do it's easy to figure out how to break the game. Buff spells don't even take up a turn so that annoyance is struck out from this game. Equipment options are limited strictly to buffing your initial gear, and small buffs to your stats. Status effects are completely negligible. Bosses all have near-identical patterns and you deal with all of them in the same way.
The dungeons however, are all very well done and are perfectly paced so they don't overstay their welcome. All of them feel fresh and distinct from one another, and flow smoothly to where you'll never feel stuck.
---Audio---
Nothing to write home about but nothing particularly terrible - although there is a random, inconsequential scene which features a track with blasts some crazy hip-hop style ad libs a minute into it. Bizarre.
The voice acting is great, but for some reason it's very down the mix as even on 50% on everything else, and voice at 100%, Rain can sometimes be barely heard. Adjust accordingly to get the best out of the performance. What I appreciate the most out of the voice acting is that it is tastefully sparse - for example if Rain is performing a handjob on someone there is no voice acting to accompany it, and why should there? There is no egregious moaning for the sake of it so if Rain happens to moan or yelp it's actually impactful. So kodus for that!
---Summary---
Like I said, a lot of these things can be forgiven in the face of Rain's neutral, breathtaking, cold stare. Uryama-ya's art is impeccable! Go enjoy it, regardless of the milktoast story and easy combat!
p.s. forgot to put this somewhere it makes more sense, but the fast traveling in this game is S tier and makes getting through the game so much easier - once you have the money definitely buy the items that let you fast travel around