Fantastic Onsen - great for a single night stay. Large, and beautiful hotel, with fantastic views of the ocean.
There are two public baths - an outside bath and an inside bath. These two baths switch between the genders every day. The baths are wonderful and hot, and have great views (even the inside bath) of the ocean.
The staff are incredible and spoiled us (I'm used to staying in business hotels, and having tea brought to us, and our bags carried was a real treat). Most of them have limited English so I imagine this hotel might be a bit difficult to stay at if nobody in your party speaks basic Japanese.
Breakfast was also a treat. I particularly enjoyed the tofu!