A simple thermal spring with strong alkalinity (pH 10.0) — the slippery, skin-smoothing feel sits squarely in Japan's beauty-water family. Lightly mineralized at 134 mg/kg total dissolved solids, so the water is gentle on the body without any heavy mineral grip. The wellhead carries a faint rotten-egg whisper of H₂S, lending a quiet sulfurous accent to the otherwise colorless and transparent water.
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⁺40.5mgP10 national94%
- Calciumsettling and calming; can leave a white mineral bloomCa²⁺2.1mgP8 national5%
- PotassiumK⁺0.30mgP3 national0.5%
- 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%
- MagnesiumMg²⁺0.0000mg0.0%
- ManganeseMn²⁺0.0000mg0.0%
- AmmoniumNH₄⁺0.0000mg0.0%
- StrontiumSr²⁺0.0000mg0.0%
- ZincZn²⁺0.0000mg0.0%
- Carbonatestrongly alkaline; slippery feelCO₃²⁻23.8mgP72 national40%
- HSiO3HSiO₃⁻41.0mgP82 national27%
- Sulfate"gypsum / Glauber's salt" — vessels and wound healingSO₄²⁻22.8mgP32 national24%
- HydroxideOH⁻1.5mgP89 national5%
- Chloridetable-salt anion — coats the skin and holds heat inCl⁻1.7mgP2 national3%
- BO2BO₂⁻0.30mgP44 national0.5%
- Hydrogen sulfideHS⁻0.30mgP47 national0.5%
- FluorideF⁻0.10mgP9 national0.5%
- BromideBr⁻0.0000mg0.0%
- BicarbonateHCO₃⁻0.0000mg0.0%
- Hydrogen phosphateHPO₄²⁻0.0000mg0.0%
- IodideI⁻0.0000mg0.0%
- NitrateNO₃⁻0.0000mg0.0%
- SS²⁻0.0000mg0.0%
- ThiosulfateS₂O₃²⁻0.0000mg0.0%
- Free carbon dioxidefizz — widens blood vessels (strong above 1000 mg/kg)CO₂9.7mgP40 national
- Free hydrogen sulfide"egg" smell — opens vessels, antibacterialH₂S0.0000mg
- ArsenicAs0.01mgP24 national
- CadmiumCd< —mg
- CopperCu< —mg
- Mercurytoxic trace — part of the drinking-safety checkHg< —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.