A blend of Totsukawa Onsen's No.2 and No.7 wells, this is a sodium-led bicarbonate spring — the classic jūsō-sen style — with a salt-tinged finish from a chloride sub-type. Soft on the skin, it sits in the Japanese beauty-water family, the water colorless and clear but carrying a faint sulfur note at the source. It emerges hot, at 58 °C, among the warmer natural sources.
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
Warming
Salt forms a film on the skin that slows heat loss, so the warmth lingers long after the bath (the classic heat-keeping water, netto 熱の湯).
cold sensitivity
Cuts
Mineral-rich chloride, sulfate and sulfur waters have a long-recorded soothing effect on minor cuts and slow-healing skin.
minor wounds
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⁺440mgP74 national91%
- Calciumsettling and calming; can leave a white mineral bloomCa²⁺17.4mgP35 national4%
- Potassiumminor; matters for drinking limitsK⁺22.2mgP66 national3%
- LithiumLi⁺1.2mgP80 national0.8%
- MagnesiumMg²⁺1.7mgP31 national0.7%
- AmmoniumNH₄⁺1.8mgP80 national0.5%
- Iron (II)Fe²⁺0.18mgP30 national0.0%
- BariumBa²⁺0.10mgP51 national0.0%
- ManganeseMn²⁺0.03mgP18 national0.0%
- AluminumAl³⁺0.02mgP22 national0.0%
- ZincZn²⁺0.01mgP42 national
- StrontiumSr²⁺NDmg
- Bicarbonate"soda" — softens skin, leaves it smoothHCO₃⁻931mgP89 national64%
- Chloridetable-salt anion — coats the skin and holds heat inCl⁻293mgP64 national34%
- Fluoridetrace; drinking limits applyF⁻4.6mgP77 national1%
- SulfateSO₄²⁻3.1mgP13 national0.3%
- Hydrogen sulfideHS⁻0.48mgP50 national0.1%
- NitrateNO₃⁻0.38mgP47 national0.0%
- Bromidetrace, sea-originBr⁻NDmg
- Hydrogen phosphateHPO₄²⁻NDmg
- Iodideyellows in air; helps blood lipidsI⁻NDmg
- Thiosulfateoxidized sulfurS₂O₃²⁻NDmg
- Metasilicic acidmetasilicic acid — a natural moisturizer for silky skinH₂SiO₃18.0mgP4 national
- Metaboric acidmetaboric acid — mildly antibacterialHBO₂2.5mgP22 national
- Free carbon dioxidefizz — widens blood vessels (strong above 1000 mg/kg)CO₂26.0mgP56 national
- Free hydrogen sulfide"egg" smell — opens vessels, antibacterialH₂S0.20mgP66 national
- ArsenicAs0.0010mgP6 national
- CadmiumCdNDmg
- CopperCuNDmg
- Mercurytoxic trace — part of the drinking-safety checkHgNDmg
- 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.
- Kario K et al. Hemodynamic Effects of Hot Spring Bathing. Hypertension Research 46(3):711–720, 2023.
- 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.