Disclaimer: Haven't tried the English version, I played the one from DLsite. Also, this game is a H-on-lose, you're NOT supposed to win every fight, if you don't like that type of games, don't play.
This game is a masterpiece, just like most of this circle's games. It has great gameplay, great art, and lots of H-content. It also has many unexpected fetishes like incest, gay sex or simply the fact that 2 twins are getting fucked and embarrassed in front of each other.
Gameplay: you basically play as one of the 2 twins, the boy or the girl, and the other will be controlled by AI. Then, hordes of enemies will run at you and try to rape them, which you can prevent by shooting and laying traps. You lose if they rape both characters at the same time, which happens quite often, as the game can be quite difficult but luckily has tons of checkpoints.
Pros:
+ Completely unique gameplay
+ Lots of level variety
+ Hentai is very well integrated to the gameplay. Your heroine basically gets battle-fucked every 15 seconds.
+ A LOT of replayability (try weaker weapons etc.)
+ A LOT of H-content (about 20 animations for the girl?)
+ Difficulty is mostly well tuned, you die a lot but there are lots of checkpoints.
Neutral:
- Half of the game H-scenes are on the male shota-esque protagonist (aka gay porn) and can't be disabled. Weirdly enough, this bothered me at first but became quite enjoyable after a while (and I'm not gay so congrats to the author for converting me I guess). There's something quite erotic about seeing both sexes getting fucked at the same time by the same enemy but different hole. Still, that's half of the game content that is a bit "wasted" so neither a con nor a pro.
Cons:
- After a while it becomes a bit too easy, once you find the best weapons you almost never lose anymore, so probably better to restrict yourself to not use OP weapons (which is boring for a H-on-lose).