The nsfw rating is correct, but don't expect any action. More like peeping. The devs have stated that they do not intend to go too far with this one. Look at it like a nice visual parody novel with good storyline and the occasional fan service that gives you some skin.
Some wouldn't mind if it went a bit further in the end, but that's for the devs to decide.
To be honest there arn't many games who only reward you in the end for sticking with your favorite girl. Most, if not all, will spread the spicy stuff throughout the game. It would be nice, to see a game with a build up to the end.