salt's cation — pairs with chloride to make the water salty.
Bicarbonate HCO₃⁻
"soda" — softens skin, leaves it smooth.
Known good for
Aches & jointsstiff shoulders
Smooth skindry, rough skin
Recoveryfatigue, stress
A hot 54.9 °C simple thermal spring of the Kurokawa area. Weakly alkaline and soft on the skin, it sits on the gentle edge of Japan's beauty-water family. A generous 177 mg/kg of metasilicic acid leaves the kind of silica film that makes skin feel noticeably smoother afterwards, with a faint rotten-egg note of H₂S drifting at the wellhead.
Sampled at wellhead·Analyzed Nov 11, 2010·株式会社 同仁グローバル·Cert no. 第K10105407号
711. Gekkoju, Kurokawa Onsen (pt.3) ★★★
About the onsen:
2. Outdoor private bath by reservation. It is on the roof of a separate building on a hill. There is a view of the forest, hills, and a meadow, but the trees partly block it. Closer to night, stars are clearly visible in the sky. The water is a clear greenish color, with bubbles. Temperature is 42.
3. Cave private bath by reservation. It is fine to breathe inside. The water is a clear greenish color, slightly cloudy. The bath has three main areas:
3.1. Main bath with utaseyu, temperature 39.
3.2. Area for lying down, for one person, temperature 38.
3.3. Shallow area at the entrance, temperature 38.
30.12.2025 31.12.2025
711. Gekkoju, Kurokawa Onsen (pt.2) ★★★
The room is modern but styled traditionally, with heated floors, various cosmetics and shampoos, a refrigerator with different free drinks, and coffee. There were European-style beds, but they laid out a futon upon my request during booking. The balcony offers a natural view and has an onsen bath.
About the onsens:
1. Baths in the Ariake room:
1.1. A round outdoor bath on the balcony with a view of the forest through a fence. Three bubble jets that can be turned off. The water is clear with a greenish tint. Temperature around 41°C.
1.2. Indoor bath. The water is clear with a greenish tint, slightly cloudy. Temperature around 42°C. It's pleasant to breathe inside.
30.12.2025 31.12.2025
711. Gekkoju, Kurokawa Onsen (pt.1) ★★★
The most luxurious ryokan in Kurokawa. The cost is on average 2-4 times higher than rooms in other ryokans in the village. There are no public baths or day-use baths. Eight different rooms each with different baths. There are separate private baths available by reservation. It is a complex of various buildings on a dedicated site.
I stayed overnight in the Ariake room. I took dinner and breakfast for one. The kaiseki dinner is served in the room in a private dining area. Breakfast is served in a restaurant in a separate building on the premises. The kaiseki dinner included fugu (pufferfish). I liked everything very much. There was a funny moment with a humorous typo in the English menu: "Worm dish" instead of "Warm dish." We laughed about it with the staff, but it was rather to my advantage – a kind of signal that the establishment's priority is not English-speaking customers.
In winter evenings, the inner grounds looked gorgeous – bamboo lanterns in the style of Kurokawa were placed around. The buildings and surroundings are pleasant. There are few rooms and few guests, creating an atmosphere of seclusion.
The service was at a very high level. The staff were Japanese. I had a dedicated staff member who spoke excellent English. Moreover, using a minimal set of Japanese words I knew and used, the staff member understood without further questions my wish to hear more Japanese for immersion, and here I had a unique service experience. All new topics addressed to me started in Japanese and seamlessly switched to English until the end of the topic if he felt I was beginning not to understand. Then the next new topic again started in Japanese until I began to lose the meaning. All this was done without any awkward moments or discussion, just naturally and without inconvenience.
At check-in, two separate private baths are available for reservation in addition to the in-room bath – an indoor cave bath and an open-air bath on the upper level.
A very cool place in terms of service, great in terms of baths. Compared to public baths in the village, of course, there are cooler options, but in terms of private baths, Gekkoju is the best in Kurokawa. The official website price might seem questionable, but when you experience it in person, all doubts disappear. A top-notch place.
30.12.2025 31.12.2025
