If you are FEMALE, please do not use this place alone or even in a group! Come with a guy to LOOKOUT for you. I brought my wife and a lady friend here. While they were relaxing inside i stood outside waiting for them as i was not in the mood for onsen that day. An old Japanese man came up the hill and it looks like he wanted to use the onsen. But upon hearing the ladies chatting inside, he just stood outside pretending to stretch while trying to look into the ladies sides. The entrance to the ladies side is only covered by a flimsy see through blind that could still allow people outside to see in if you stretched your neck abit. I started staring at him and he just smiled and walked into the men’s side. But after a few minutes, i felt suspicious and decided to see what the man was up to. Turns out he was buck naked and peeking over the rocks at the ladies. I then shouted at him, and he quickly came out of the onsen, put on his clothes and hurried away apologising.
With all that, it is still a nice little charming free public onsen out in the hills. The water is milky and very mineralised so i guess it is good for the skin. It is separated by a wall of rocks each side for men and women, with a little hut on each side for you to change. There is no toilet or shower facilities.,There is no view except for the forest surrounding the onsen, so you are just getting the experience of a free outdoor onsen on a hill in the middle of nowhere. You can purchase towels at the shop below before climbing up to the onsen or bring your own. For those who can’t read Japanese, take the left lane up, the right lane leads to a hiking trail.
It is their culture to be naked when using onsen, but i would suggest ladies to wear a swim suit as there are peeping toms there. Or come with a trusted guy to stand guard for you.

Currently all outdoor pools are closed but surroundings looks besutiful
It was my first ever open-air bath. I went in the fall, and from the moment I drove there, it was foggy, there were hotel-like buildings (I don't know if they're still in operation), and then I drove up a road that seemed to lead into the mountains. Because I have a fear of heights, I was out of breath, and the fear of encountering a bear created a double dose of terror, a Silent Hill-like feeling. The whole experience was amazing.
It's a vivid memory.
I saw a few foreigners, and I'm really curious how they got there...
Assuming the hot spring water varies from day to day, there were a lot of mineral deposits scattered in the water, but not a large accumulation of them. Instead, there was a vibrant emerald green accumulation, which made me anticipate the composition of the water. The water itself was like a diluted version of Shirahone, but the emerald green accumulation was intriguing. It had a light sulfurous smell and wasn't viscous. It had almost no taste.
But, all in all, the feeling of being in the open air, including the journey there, was incredibly thrilling.
I was able to enjoy the free open-air bath, "Ougon-no-Yu," without encountering any of the "spring bears" that had surprised me so much near Sekiyama Station. It was reassuring that it was separated for men and women.
It was great, absolutely wonderful.
For 30 years, I've been told by many that this hot spring is excellent, and I finally went there, fulfilling a long-held wish.
The autumn leaves hadn't changed color yet. The location was a bit scary, as it felt like a bear might suddenly appear from the bushes along the way. All the hikers going up were wearing bear bells, which made it even more frightening.
The bathwater was cloudy but smooth.
Apparently, there are insects in the summer, but by late October, there were no insects, making it very comfortable.
The cool outside allowed for a long soak, and there were few other bathers, perhaps because the leaves hadn't changed color yet, making it very pleasant.
A perfect hot spring.
There were some foreign guests with me, and they seemed unsure of the procedures, so I managed to explain things in my broken English, resulting in a mini-international exchange.
I'm grateful to the local people who manage this wonderful hot spring!