An alkaline simple thermal spring (pH 8.9) sitting squarely in Japan's beauty-water family — the high pH gives the characteristic slippery feel on the skin. At the wellhead the water carries a faintly salty tang and a whisper of hydrogen sulfide; emerging at 36.7 °C, it is pumped up rather than free-flowing and would normally be reheated. Lightly mineralized at 475.7 mg/kg, the chemistry is gentle and undemanding — a soft, easy soak rather than a strong-mineral plunge.
Good for
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⁺79.1mgP25 national55%
- Calciumsettling and calming; can leave a white mineral bloomCa²⁺55.1mgP59 national44%
- PotassiumK⁺1.0mgP14 national0.5%
- StrontiumSr²⁺0.20mgP44 national0.2%
- MagnesiumMg²⁺0.10mgP11 national0.2%
- AluminumAl³⁺0.0000mg0.0%
- BariumBa²⁺0.0000mg0.0%
- CopperCu²⁺0.0000mg0.0%
- Iron (II)Fe²⁺0.0000mg0.0%
- Iron (III)Fe³⁺0.0000mg0.0%
- HydrogenH⁺0.0000mg0.0%
- LithiumLi⁺0.0000mg0.0%
- ManganeseMn²⁺0.0000mg0.0%
- AmmoniumNH₄⁺0.0000mg0.0%
- ZincZn²⁺0.0000mg0.0%
- Sulfate"gypsum / Glauber's salt" — vessels and wound healingSO₄²⁻249mgP70 national79%
- Chloridetable-salt anion — coats the skin and holds heat inCl⁻28.2mgP21 national12%
- Bicarbonate"soda" — softens skin, leaves it smoothHCO₃⁻11.9mgP7 national3%
- FluorideF⁻0.60mgP38 national0.5%
- Hydrogen phosphateHPO₄²⁻0.0000mg0.1%
- SS²⁻0.0000mg0.1%
- BromideBr⁻0.0000mg0.0%
- Hydrogen sulfideHS⁻0.0000mg0.0%
- IodideI⁻0.0000mg0.0%
- NitrateNO₃⁻0.0000mg0.0%
- HydroxideOH⁻0.0000mg0.0%
- Metasilicic acidmetasilicic acid — a natural moisturizer for silky skinH₂SiO₃37.5mgP19 national
- Metaboric acidmetaboric acid — mildly antibacterialHBO₂2.9mgP24 national
- Free carbon dioxidefizz — widens blood vessels (strong above 1000 mg/kg)CO₂75.0mgP75 national
- ArsenicAs0.13mgP69 national
- CadmiumCd< —mg
- ChromiumCr< —mg
- CopperCu< —mg
- LeadPb< —mg
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.
- 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.