Many supersento don’t use their ample space efficiently. Many supersento say they have a natural hot spring, and while they aren’t lying, but the quality of the spring is no better than tap water. Oka no Yu in rural Asago City is the shining example of what a rural supersento should be.

The water is very alkaline and feels smooth to the touch. The incredible feel of this water is instantly noticeable. If you gently run your and along your body it is smooth but if you put a bit of pressure your hand stops as if you had a gecko's toes. Almost every bath takes advantage of the spring, even the wash basins. There’s a sign on the wall warning people with weak skin to use the normal tap water showers rather than the basins. Although if you have weak skin there are not many options for you other than the saunas and cold water bath.

Indoors the baths have a basic supersento feel. All the materials are of good quality. It’s the rotenburo area that really shines. It’s pretty small, but there are many baths to explore. The tub baths are located in a shallow foot bath area. Each of the tubs are made of beautiful pottery and overflow into the foot baths. The feeling of stepping out of the warm foot bath into the hot tub is absolutely wonderful. There are three tubs to choose from and all are big. One could fit 3 people or let a single adult male stretch out.

The communal bath has a upper and lower part. The temperature felt the same however. The lower one is shallower and has better view of the TV. The upper one has a more secluded feel. The rocks used to make this bath, especially the large stone used as a stair inside the bath, are all beautiful and well chosen.

Outside there is also a great steam sauna. It was so steamy in there I could barely see my hand in front of my face.

Oku no Yu has two bad points. The website is all done in flash and thanks to a popup blocker won’t open in Chrome. I had to open it in Safari. Second, it’s really rural and they are not use to seeing many foreigners there. At least I had that impression as the staff tried to speak English to me and seemed to treat me with a bit of extra care. The parking lot attendant was quite funny though and I enjoyed chatting with him for a few seconds when I entered and left.

They seem to be very, very worried about people taking photos in the building as there were many new looking signs about it. Be extra careful about using your phone.

If you plan on walking from Wadayama Station as I did, make sure to give yourself ample time, at least 20 minutes or more. The walk is pleasant and offers many great views of the trains coming and leaving the station, but if you are trying to make the next train you might have to rush it as I had to.