A lightly mineralized simple cold-mineral spring (21.5 °C at the wellhead) that qualifies as an onsen on its metasilicic acid content. Total dissolved solids are a modest 0.479 g/kg and the water is weakly acidic and gentle on the body. With 94.4 mg/kg of metasilicic acid it sits in the Japanese beauty-water family, leaving a thin silica film that makes skin feel smoother. A faint hydrogen sulfide note rises at the source.
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.
- Calciumsettling and calming; can leave a white mineral bloomCa²⁺48.2mgP57 national50%
- Sodiumsalt's cation — pairs with chloride to make the water saltyNa⁺23.7mgP5 national21%
- Magnesiummild; a laxative if you drink itMg²⁺12.4mgP64 national21%
- Iron (II)rusts brown in air; iron for anemia when drinkableFe²⁺9.1mgP86 national7%
- PotassiumK⁺1.7mgP19 national0.9%
- StrontiumSr²⁺0.50mgP68 national0.2%
- BariumBa²⁺0.10mgP53 national0.0%
- Aluminumshows up in acidic volcanic waterAl³⁺< —mg
- Iron (III)Fe³⁺< —mg
- Hydrogenmakes the water acidic — sharp and bactericidalH⁺< —mg
- LithiumLi⁺< —mg
- Manganesetrace; companion to iron springsMn²⁺< —mg
- Bicarbonate"soda" — softens skin, leaves it smoothHCO₃⁻283mgP64 national97%
- Chloridetable-salt anion — coats the skin and holds heat inCl⁻4.4mgP6 national3%
- SulfateSO₄²⁻1.3mgP8 national0.6%
- BromideBr⁻0.10mgP15 national0.0%
- Carbonatestrongly alkaline; slippery feelCO₃²⁻< —mg
- Fluoridetrace; drinking limits applyF⁻< —mg
- Hydrogen phosphateHPO₄²⁻< —mg
- Hydrogen sulfidesulfur character — antibacterialHS⁻< —mg
- Iodideyellows in air; helps blood lipidsI⁻< —mg
- NitrateNO₃⁻< —mg
- Thiosulfateoxidized sulfurS₂O₃²⁻< —mg
- Metasilicic acidmetasilicic acid — a natural moisturizer for silky skinH₂SiO₃94.4mgP53 national
- Metaarsenious acidHAsO₂< —mg
- Metaboric acidmetaboric acid — mildly antibacterialHBO₂< —mg
- Free carbon dioxidefizz — widens blood vessels (strong above 1000 mg/kg)CO₂129mgP83 national
- Free hydrogen sulfide"egg" smell — opens vessels, antibacterialH₂S< —mg
- ArsenicAs< —mg
- CadmiumCd< —mg
- ChromiumCr< —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.