I find that I agree with oneupthextraman. The story situation and the history getting us to this point is really fascinating and fun, it makes so much sense, it is so easy to see and follow how society, the desire to show how wealthy you are, and fashion could all combine to produce a result like this.
There are various examples through history of people living with things that made their lives very difficult, to show their status, so the idea really makes sense. The first part is fun and sexy, I really liked and enjoyed it. Watching how her place in society calls for, and rewards such bondage, and how very elegant and decorative it has become, all while done by a loving and supportive fiancée.
But as parts 2 and 3 went on, I did find the increasing harshness, the simple evil for the sake of watching someone helpless to escape being punished didn't really work for me, or offer so much pleasure or enjoyment. At least not everyone is into treating Nin so badly, but those evil nipple clamps? That really wasn't nice.