Good old Megami Ero. Rather old one, but actually pretty good. I id beat it a long time ago, but lost the savefile. The actual gameplay is way more interesting than the sex scenes.
FYI, the last part of the game is a maze which is actually nigh-unsolvable without a walkthrough because it includes looping parts. Sadly, the walkthrough of the maze was only found somewhere in the author's forums comments, and has since been buried by a mass spam attack

Fortunately, the game is vulnerable to right click exploiting... which most times simply messes the game up, but fortunately it can be used in the maze to jump to the next battle, and from it to the game end. (Hey, don't look at me that way. You know I love to dissect the games as much as I love playing them)
