I'm surprised this little gem of a H-game hasn't been mentioned on here.
You play Lars, who, along with his two allies, has managed to make his way to the lair of the evil demon lord. You fall in battle, and find yourself in the basement, except there appears to have been another battle...
You get to the throne room, to find succubi have claimed the castle for themselves, and, when you fight back, they claim Olivia, one of your allies, as well. You flee, but not long after discovering there is a way to defeat the succubi...
This game starts well and goes on well. Faces and battle sprites are done with high-detail, high-resolution graphics, and only the map screen uses the original RTP system, with custom menus and battle graphics.
The only annoyance is that it is a japanese game, so english gamers will get blank areas in most of the text boxes, and some of the most useful information is unreadable.
Anyway, It's a good game, marred only by it's lack of a english language option... Maybe, one day, RGSSAD files won't be so hard to open, and we can maybe translate such gems as this...