The benchmark for H-Games being considered "excellent" is a fairly low one. Most games out there are complete trash which not only fail to put out decent content, but are travesties of games rather than games themselves. In this sea of shit, Nightmare Knight comfortably stands out as one of the highlights in the corruption genre. If you've played Shimobashira games like Celesphonia and Ambrosia before, this will feel fairly similar. However, there are some additions that make this better, and some that make it worse. Overall though, for a fan of the corruption genre, this is well worth a play. What the game has - battle-fuck, night and day system, fair few scenes in the town itself, some minor NTR, clothing damage, cosplay i.e. the usual trappings.
The story in H-Games, as I keep on repeating, is usually bullshit. All you just want is that it frames the content reasonably, as in gives a reason for it. This is especially important in corruption games as you want a reason to go out and slut out the heroine. Nightmare Knight does this fairly well. Lust curse, losing reason, blah blah blah. It's understandable why she gives in.
The gameplay aspect is where there are serious missteps. One - combat is ridiculously easy for all battles. You probably don't even need to level up so the battle-fuck is severely underutilized. You can annihilate most bosses in 4-5 turns as well, often without even giving them a chance to attack. The battle system isn't interesting or new. Whereas better games add variety by at least including enemy resistances and strengths and a wide variety of spells to satisfy your fancy, there's none of that here. But it's passable. The other misstep is that corruption requires some sort of coercion. Some need to earn money, garner resources. There's none of that here. You will have so much money you'd practically be drowning in it. It's also unfortunate that you get free housing so can't even think "Oh, need money for the inn and I don't have money so need to sleep in the seedy inn the slums". So yeah, could be better there. The third misstep is that desire is way too easy to keep in check. You will almost never have an occasion where your meter is filled if you haven't gone out and deliberately lost every battle and picked all the wrong choices. (which is dumb, in my opinion, you should never reward playing poorly. I came here for the game, not just the content). This is a problem because in the final battle, you have to choose Desire to get a certain end and I had none. HA. Which ironically meant I got a bad end. And the last misstep, which is also a bit criminal, is that a lot of content is stuck behind story progression. You can't access the casino until you unlock the last dungeon. This means for a lot of the time, you have nothing to do apart from progressing the story. Which means fewer chances for corruption. Which means less fun for me. There also isn't a lot of content in the city (the beach also is horribly underutilized). Lastly, going full Lust Mode or Climax Mode has little to no benefits or detriments. I can still steamroll most enemies, reactions of people don't differ. You can play the game as is. Which is again, a horrible underutilization of such an interesting concept.
There are still things which are done well. For one, I love the idea of the Desire bar and having a QTE at key intervals to choose Desire vs Reason. It could have been used more but as is, it's still pretty good. The art is also stupendous. Censored and all that, but it's what we've come to expect. There's also a fair bit of CGs, even if the scenarios aren't novel. I like cosplay even if it isn't used all that much in the game itself.
I know the review sounds more like negatives and barely any positives. But there isn't exactly groundbreaking work in H-Game genre. This game satisfies the bare minimum (decent combat and great CGs). While it also has some novel ideas like the QTE traps and Desire vs Reason bar. So it does everything you want an H-Game to do well. My complaints revolve around what could have made it even better. Nonetheless, well worth the 4-8 hours you'll spend.