A sodium-led alkaline simple thermal spring with a remarkable slippery feel on the skin — pH 9.5 at the wellhead rising to 9.8 in the lab, squarely in the strongly alkaline range that defines Japan's beauty-water family. Lightly mineralized at 152 mg/kg, so the water is gentle and unobtrusive on the body. A faint rotten-egg note of H₂S and a hint of sulfur on the tongue emerge straight from 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.
- Sodiumsalt's cation — pairs with chloride to make the water saltyNa⁺38.7mgP8 national90%
- Calciumsettling and calming; can leave a white mineral bloomCa²⁺3.5mgP13 national9%
- PotassiumK⁺0.30mgP3 national0.5%
- Aluminumshows up in acidic volcanic waterAl³⁺< —mg
- FeTotalFe< —mg
- Hydrogenmakes the water acidic — sharp and bactericidalH⁺< —mg
- Magnesiummild; a laxative if you drink itMg²⁺< —mg
- Manganesetrace; companion to iron springsMn²⁺< —mg
- Carbonatestrongly alkaline; slippery feelCO₃²⁻29.4mgP82 national50%
- Chloridetable-salt anion — coats the skin and holds heat inCl⁻13.1mgP15 national19%
- Fluoridetrace; drinking limits applyF⁻5.2mgP79 national14%
- Sulfate"gypsum / Glauber's salt" — vessels and wound healingSO₄²⁻13.0mgP25 national14%
- Bicarbonate"soda" — softens skin, leaves it smoothHCO₃⁻1.8mgP2 national2%
- Hydrogen sulfidesulfur character — antibacterialHS⁻0.90mgP69 national2%
- BO2BO₂⁻0.40mgP48 national0.5%
- HSiO3HSiO₃⁻< —mg
- HydroxideOH⁻< —mg
- Thiosulfateoxidized sulfurS₂O₃²⁻< —mg
- Metasilicic acidmetasilicic acid — a natural moisturizer for silky skinH₂SiO₃45.8mgP26 national
- Metaboric acidmetaboric acid — mildly antibacterialHBO₂< —mg
- Free carbon dioxidefizz — widens blood vessels (strong above 1000 mg/kg)CO₂< —mg
- Free hydrogen sulfide"egg" smell — opens vessels, antibacterialH₂S< —mg
- CadmiumCd< —mg
- CopperCu< —mg
- Mercurytoxic trace — part of the drinking-safety checkHg< —mg
- LeadPb< —mg
Measured at the source
On the certificate
- 神経痛
- Muscle pain
- Joint pain
- Frozen shoulder
- Motor paralysis
- Joint stiffness
- Bruises
- Sprains
- Chronic digestive disorders
- Hemorrhoids
- Cold sensitivity
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.