Well, pain would probably be fine as long as it didn't go too far. The game runs the gauntlet of M fantasies. You've got tame stuff like word play, all the way up to crazy shit like unbirthing and vore. I'd say as long as it doesn't get to the level of bleeding or actual physical injuries, you'd be right up Luka's alley.
Personally I played the game for the plot (no, seriously, the plot is actually good) so I only experienced about a third of the H-scenes, but I'm fairly sure a few of them were bondage-y.