Jomontennen Onsen Shiraku No Yu

This is a really cute, rustic onsen for day use, with a lovely atmosphere and deep yellow water. It isn't sparkling clean, but the outdoor bath was wonderfully hot, about 42C, and the sauna was great at around 100C. The staff were friendly. For visitors who don't speak Japanese, access seems probably alright: the main sign for the men's and women's bathing areas is translated, and the staff can likely help with the rest. It's surprisingly easy to reach from Shinagawa station, about 25 minutes with one transfer and trains every 10 minutes. Could work well during a longer wait for a Shinkansen. The indoor bath was out of order today because of a defect, but the outdoor bath and sauna were plenty.

According to the onsen guide, this place's story begins as a Jomon forest, later turned into rice paddies, and eventually into a site for cutting-edge manufacturing. In early summer 2005, they decided to bring the land back to its Jomon forest state. While digging, they unexpectedly found a natural hot spring close to 40°C. They brought andesite from the Yatsugatake Mountains in Shinshu and natural wood from Hiryuno in Kyushu. Japan's number one bath-building expert, the late Tetsuya Goto of Kurokawa Onsen in Kumamoto, lovingly built the open-air bath. The guide describes the place as holding the Jomon spirit, the roots of Japanese identity and harmony. It calls it a hometown in the city, born from the red of Japan's cultural revival, and speaks of the spirit of its founding.

The staff and people here were really friendly to me as a foreigner, even though everyone else seemed to be local. The baths were great too. If being naked makes you hesitate, don't let that keep you from enjoying this.

Such a fantastic experience, and it really feels like a local gem. I was the only foreigner there. The sauna is fiercely hot, like a volcano, and the pools are so relaxing. One of the best things I've done in Japan.