If you want a traditional hot spring, this isn't it, but it's a wonderful place for a day trip. They have a variety of baths with the essences of things like wine, green tea, and sake mixed in, as well as a swimming pool, sauna, some little water slides and a splash zone for the younger crowd, and massages which you can pay extra for. Honestly, the most relaxed I ever felt while in Japan was after leaving Yunessun.
If you're self-conscious, don't worry, most of the springs require everyone to wear bathing suits. However, if you're feeling up to stripping down, there is also a public bath in the basement. Highly recommended.

There are many hot springs in Japan, but this one is a must see. The drive alone takes you through the misty narrow cliffs around Mt. Fuji. You can bathe in the indoor area where they have little fish who eat away at the dead skin on your feet. Thats a little to creepy for me, I would rather get a pedicure! Or outside the natural springs are set on the side of a mountain and have saki and green tea baths. The best is Mori No Yu, the female only nude bathing area. It is outside and you can see the beauiful mountains. The architecture is amazing and you can sit in your own personal wooden tub of hot spring water.