Izu Mitaka-Iriya Kogen Onsen
Izu Mitaka-Iriya Kogen Onsen is a little-known 100% pure hot spring located at the border of Kawazu city and Inatori city.
There is a cottage where you can stay overnight (there is no meal service). (You are allowed to bring your own food and ingredients to cook)
There is also a shop which sells local produce as well as a rest area in the spa facility. Wood that was cut in the nearby mountains was used for the cottage building.