Way, way back, I bought this through a guest log-in; at some point, I lost the file, and since I had an account by then, I went ahead and bought it again. It's that good.
Almost every aspect of this game is spectacular. The gameplay is challenging and interesting enough that it'd be fun even without hentai; there are a number of difficulty modes, ramping up from super-easy to extremely hard. Certain enemy attacks damage Iris's clothes, destroying her blouse, skirt, or panties, and you can see her increasing embarrassment as she's stripped, shown by her expression in an on-screen portrait. When you run out of life, on-screen enemies will ravish Iris until you choose to continue or view the game-over animation--and every one of those is detailed, varied, and beautiful. One nice touch is that there are up to six possible animations for (almost) every enemy, reflecting Iris's state of undress when you lost. What's particularly nice is that the animations aren't just the same loop with different clothes; some are significantly different depending on what Iris is wearing. Even better, they're not just a simple repeating loop, but have random voice-acting and motion cycles incorporated. There are a couple of ryona options, too; if you let her get pummeled before viewing the game-over screen, some enemies have a second, beat-up-Iris set of animations.
Literally the only legit complaint I have is that the tall grass in Stage II obscures some of the on-screen action after you've lost; I would gripe that there's no English translation, but that's just icing on the cake for a game like this.
Bottom line is that if you like side-scrollers, some ryona, tentacle/monster/zombie/ghost/weirdo/devil-dog/plant/insect rape, and good gameplay, this is a 100% winner. Buy it at full price, just to give the maker his due!