tl:dr - A fantastic RPGmaker game, with an innovative combat system, where you manage desires and use a rock-paper-scissors style counter to enemy stances, tons of choices, and great CGs.
Karryn's Prison is an RPGmaker game, and that already doesn't sound good. However, instead of playing in some grand, empty open world, you play in a prison. There are five levels to this prison (2 fully implemented, third missing boss/subjugation) and you must manage each level that you conquer.
The story is basic, but it is well written. You're the king's secretary, and you are sent to this overthrown prison in an attempt to regain control. Karryn is hesitant to actually go in, but she does what the king says. She is a headstrong, confident, and arrogant warden, but she is effective. Other than that, there's not much more to the story. There's some grand villain that orchestrated the uprising in the prison, but that's it. If you're looking for a fantastic, engaging story, with branching paths, this might not be the game for it.
The gameplay of KP is quite good, as it makes the player think before making an attack. Every enemy in the game has three stances - red, yellow and blue. Red counters blue, blue counters yellow, and yellow counters red. It is essentially Pokemon, but that doesn't make it bad. In fact, once you encounter more than 2 enemies, you really have to think about which enemy to knock out first, which stance you will end up in, and if you want to use any supporting abilities. That's another key part of KP - the wide variety of abilities you can get. Each color has one basic attack, and two unlockable ones. Each color focuses on something different, like red focuses on singe-target burst, while yellow focuses on AoE.
Another part of combat is managing desire. Desire is how much Karryn wants something perverted. This is shown in small, pink hearts. There is mouth, butt, cock, etc. If a desire is high enough, then enemies can do a grope or sex attack. A grope attack will play a very short 1-2 second animation, and it will further increase desire and also pleasure. If pleasure reaches 100%, Karryn orgasms, and cannot do anything for a turn or two. Desires aren't that difficult to manage, since you use another resource called "willpower" to simply suppress specific desires. If desire goes too high, then Karryn may be forced into a sex scene. These still play in the actual gameplay, rather than go to a text box. They are very well drawn, but lack animation. This is one of the better parts of the game, as you don't have to lose a battle to see CG. However, there are still a few post-battle CGs you can only get by losing.
Passives are another vital part of the gameplay, and they are well implemented. Passives, generally speaking, will increase Karryn's slut level. These passives can be achieved through getting groped X number of times, getting creampied X number of times, and so on. They will also make her weaker to sex and grope attacks, which means you unlock more passives, and there are a LOT. There is somewhere around 300+ passives currently in the game. Some are mutually exclusive, some aren't.
Edicts are a way to improve both the prison, as well as Karryn. There are ones that affect only Karryn, like giving her more strength, agility, etc., or ones that impact the prison, like a lower chance of riots, more income, and so on. Most of them are unlockable, but a few are mutually exclusive. They also add a lot of choice in regards to how to approach the prison. Do you go for the riskier route, with a high chance of riots but more money, or do you go for the safer path, where you make less money but riots are less likely? There is probably an optimal path for these edicts, but having choices is the fun part.
Last up is difficulty. I'm not a fan of how it is implemented. There is Secretary, Warden, and Prisoner difficulty. Secretary is the easiest, which allows manual saving, increased income, lowered enemy stats, etc. Warden is kind of a medium difficulty, and offers a fair balance between easy and hard. Enemies do normal damage, you don't get a boost to income, and you will have to think a bit in order to succeed. However, the biggest issue I have with this is that you cannot manually save. This means that, every time you enter a room, the game autosaves. That means if you make a big mistake, then you cannot reload to a previous save. This also goes for prisoner mode, which gives you smaller income, stronger enemies, and so on. If saving was allowed on Warden difficulty but not Prisoner, then that'd be fine, but that's not the case. The only good part is that if you lose the prison (which can only happen if your order falls to 0), then the game takes you back to the difficulty selection screen, but allows you to keep your levels and passives. You can also lower the difficulty by 1 level.
In conclusion, Karryn's Prison is definitely worth playing. It has some issues in regards to difficulty and the grind, but the great CG, innovative gameplay, and overall art makes it a must-play. Even if you aren't a fan of RPGMaker games, at least try this one!