This is a great game, far better than one would expect. The story, although somewhat difficult to take at face value, is rather interesting. The presented characters are well made, and not as simplistic as most H games have them.
The slate demon is prideful, but not arrogant, and even though he consider himself better than humans, he won't go into a fit of rage for being defeated in his game. Instead, he recognizes the hero's ability.
The princess starts as the usual bitchy, arrogant princess. But there's room for change in the game, with 3 endings (and a game over for being overly rough) deppending on how you treat her. Except the bad one, the endings are not as simple as expected, and surprisingly satisfying. I played this game for the slave ending, but the love ending satisfied me more.
The sex game mechanic is honestly well made. Slowly building the girl's interest, making her comfortable and then taking her first time as painlessly as possible, so she'll love having sex.
Be too rough, and she'll hate it. If you can't satisfy her, she'll be unhappy. Make her cum until she's satisfied and she'll be a good girl. These 3 happen in real life too lol.
Really, great game.