An alkaline simple thermal spring at pH 8.9, sitting in the Japanese beauty-water family with the characteristic slippery feel. Mineralization is light (289 mg/kg dissolved solids), so the 56 °C source reads as gentle and easy to soak in rather than mineral-heavy. The water itself is nearly colourless, tasteless and odourless — the appeal is the soft, smooth feel on the skin rather than any sensory signature.
Good for
Aches & joints
Warmth eases stiffness and raises the pain threshold. Radon and sulfate springs show the strongest evidence for joint and muscle pain.
stiff shoulders
Smooth skin
Bicarbonate and alkalinity gently lift dead keratin while silica hydrates, leaving skin smooth. This is the basis of the beautifying-water (bijin-no-yu 美人の湯) reputation.
dry, rough skin
Recovery
Warmth and buoyancy lower stress markers and improve sleep; habitual bathing is linked to lower rates of depression.
fatigue, stress
Full composition
The bar is each ion's share of charge (mval%) within its group; over 20% names the spring. Gases, silica and trace metals are measured by mass only.
- Sodiumsalt's cation — pairs with chloride to make the water saltyNa⁺76.0mgP24 national90%
- Calciumsettling and calming; can leave a white mineral bloomCa²⁺6.1mgP19 national8%
- PotassiumK⁺1.4mgP17 national1.0%
- AluminumAl³⁺0.07mgP33 national0.2%
- Chloridetable-salt anion — coats the skin and holds heat inCl⁻66.6mgP32 national50%
- Bicarbonate"soda" — softens skin, leaves it smoothHCO₃⁻61.1mgP33 national26%
- Sulfate"gypsum / Glauber's salt" — vessels and wound healingSO₄²⁻24.1mgP33 national13%
- Carbonatestrongly alkaline; slippery feelCO₃²⁻11.2mgP52 national10%
- FluorideF⁻0.80mgP44 national0.8%
- Metasilicic acidmetasilicic acid — a natural moisturizer for silky skinH₂SiO₃40.9mgP22 national
- Metaboric acidmetaboric acid — mildly antibacterialHBO₂1.2mgP13 national
- ChromiumCrNDmg
- CopperCuNDmg
- Mercurytoxic trace — part of the drinking-safety checkHg< —mg
- LeadPbNDmg
Measured at the source
Evidence
- Maeda M. 温泉の医学的効果とその科学的根拠. J. Hot Spring Science 70:197–207, 2021.
- Naito Y et al. A Hot-Spring Water Improves Inflammatory Conditions in an Atopic Dermatitis Model. Biomedicines 13(11):2707, 2025.
- Donaubauer AJ et al. Serial radon spa therapy on pain in musculoskeletal disorders. Frontiers in Immunology, 2024.
- Verhagen AP et al. Balneotherapy for rheumatoid arthritis. Cochrane Database of Systematic Reviews CD000518, 2015.
- Li H et al. Bicarbonate Ionized Water Bathing Enhances Natural Killer Cell Activity. Scientific Reports 14:51851, 2024.
- Takeda M et al. Hot spring bathing practices have a positive effect on mental health in Japan. Heliyon 9(9):e19631, 2023.