Nowhere else, this is what I mean by a magical sauna.

development
3-21 Honmachi, Haramachi-ku, Minamisoma-shi, Fukushima
hattatsu.jp/
Fee: ¥23,800 (for 5 hours use, for a single building rental)
Sauna Thailand. It is a well-known sauna review site. The site includes information such as the temperature of the sauna room and water bath, whether or not an outside air bath is available, and even the impressions of those who have experienced it, so it is extremely reliable when looking for a sauna in an area you have never been to before. I was surprised to see so many small saunas. You may be surprised to find reviews of even the smallest saunas.

The "Kaihatsu-kun doll" placed at the entrance adds to our mystery.
However, the sauna "Development" visited at the end of this trip had zero reviews as of early October 2021. In this networked society, the lack of information is unsettling.
Shibayama, are you really, really okay.... With this in mind, I visited Minamisoma City.
As soon as I see the sauna here, my head is filled with "? come to mind as soon as I see the sauna. The neon-lit cave-shaped sauna, the countless masks next to the water bath, the heat wave master who is a former sumo wrestler, the restrooms with manga scenes covering the walls... I have never seen anything like it anywhere else. It doesn't feel like it was built based on anything at all. It's as if the magnetic field has gone crazy.
First of all, what is "development" that I am most interested in? I asked the owner, Mr. Kawaguchi, and he answered that it is a concept beyond "tonou.
The "?" in my head was not resolved at all, and the story continues. Mr. Kawaguchi used to go on stage to become a comedian. However, at some point, he realized that he would be happy if he could make the people around him smile, not just someone unspecified. This was the turning point that changed his outlook on life.

Mr. Kawaguchi's way of life seemed to be the opposite of Steve Jobs' legendary speech, "My past experiences connect the dots and naturally become a line (I'm leaving out a lot). In order to forcibly create dots, he has set himself a rule that he starts one new thing a year that he knows nothing about.
For example, in his first year of business, he started an izakaya without even knowing how to make a watered-down version of sake, and was even beaten over the head by a customer for serving sake watered down. That is how full of the "do it yourself" spirit he is.
So one year, I went to Kumamoto to learn about a reasonable building construction method. That was the earth-back construction method used for "development. Known among hippies and other alternative people, this method was born from a novel idea of combining earth-friendly soil and clay materials with modern construction techniques. And after being baptized and inspired by the sauna at Yurakkusu, also in Kumamoto, Mr. Kawaguchi returned to his hometown of Minamisoma.
When he delved deeper into the earth-back construction method with the idea of creating an original sauna, he learned that the far-infrared ray effect of earthen walls is exceptionally high, making them suitable for saunas. This was the moment when the dots became lines, and the cave sauna was born.
When I was allowed to experience the cave sauna that was created by such a coincidence, "? turned into "! to be more precise, "? To be precise, "? I don't care what you think. The common phrase, "Feel rather than think," echoed through my brain. The temperature was so high that one could not experience it in a normal sauna. But don't think about the temperature, just feel it. Don't worry about the clock, just stay as long as you can stand it," I thought to myself. Perhaps this is where saunas originated... it makes you feel that way. After the sauna, a water bath under the watch of a mask, and an outdoor air bath on the deck while looking up at the stars, you can only describe it as "developmental. It is a sensation that melts your brain.
Incidentally, Mr. Kawaguchi's wild episodes are always interesting. There are many stories that cannot be included here, so please visit "Kaihatsu" and listen to what he has to say. This is not an appropriate way to end a visit to this sauna. All saunas, go to Minamisoma for a taste of "Development". Feel the pleasure that lies beyond "totonou".