Ofuro Cafe (Bath Cafe) offers Japanese bath and spa treatment followed by healthy Japanese food. It's open all night, so you have an option of staying until the morning if you prefer. There are shelves filled with books (that you can take into the baths!), saunas, massage rooms, a cafe, quiet sleeping rooms, and even hammocks. Everything you could ever need for the ultimate relaxation experience is here.
The baths are less impressive than a regular onsen-only facility, but they do not feel lacking. There is an outdoor bath, cold bath, some indoor jet baths, a main indoor bath, electric bath, and a sauna.
In the lounging area there is a restaurant, a fire pit, comfy chairs and mini sofas with blankets you can use, a reading area, and an area filled with massage chairs.
It is closest to the Tetsudo Hakubutsukan Station on the New Shuttle Line. The New Shuttle Line is a dinky line that runs from Omiya station. It seems like an inconvenient line, and is a bit far when you are coming from Tokyo.