This was our first trip to Japan, ever, so we wanted to experience authentic and traditional Japanese hospitality, and what an amazing surprise we got.
We rented the suite, which is the annex. You basically get an entire traditional japanese house, with a private onsen, all for yourself.
From the moment you arrive to the ryokan, you get the warmest welcome you can imagine. You are taken to your guest house and introduced to everything around a house. They provide you with Yukatas so you can feel comfortable.
For dinner, they come and serve you like a 5 or 6 course meal (I can't remember exactly how much they were), fully authentic seasonal japanese food. Once you are done, they come pick up the food from your dining room, and set up the futons were you will be sleeping, really comfortable futons.
By morning, they come and serve the breakfast and store the futons.
Did I mentioned the amazing private onsen all for yourselves? What an amazing experience onsens are. Now I understand why it is so embedded in Japanese culture.
The only thing I regret is not staying another night, since we had a very tight Japan schedule. But if you ever go to Japan, at least once stay in a traditional Ryokan to enjoy tradition. And I cannot emphasize how great a decision would it be to choose Nanten-en. And if you can afford the suite, go for it. It is something you need to experience once in a lifetime at least.