A sodium-led bicarbonate-chloride spring drawn from the Yadori Tamagawakyo source. It is the classic juso-sen style, and an alkaline pH gives it the soft, slippery touch of Japan's beauty-water family. The water is colorless and clear, yet it carries a trace of hydrogen sulfide in both smell and taste — an extremely faint sulfur note that is this spring's signature. The posted analysis documents this particular water for cuts, peripheral circulation disorders, cold sensitivity, depressed mood and dry skin. It reaches the baths heated to a comfortable soaking temperature and undiluted; the indoor bath pairs recirculation with free-flow source water, and chlorine-based disinfection is used to meet the prefectural hygiene standard.
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
Take care
- Active stage of any illness (especially with fever)
- Active tuberculosis
- Marked physical debilitation, such as advanced malignant tumor or severe anemia
- Severe heart or lung disease causing breathlessness on slight exertion
- Severe kidney disease with edema
- Gastrointestinal bleeding
- Visible bleeding
- Acute exacerbation of a chronic illness
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⁺318mgP65 national
- Calciumsettling and calming; can leave a white mineral bloomCa²⁺5.0mgP17 national
- Potassiumminor; matters for drinking limitsK⁺4.5mgP33 national
- FeTotalFe1.8mgP81 national
- Aluminumshows up in acidic volcanic waterAl³⁺< —mg
- Hydrogenmakes the water acidic — sharp and bactericidalH⁺< —mg
- Magnesiummild; a laxative if you drink itMg²⁺< —mg
- Manganesetrace; companion to iron springsMn²⁺< —mg
- Bicarbonate"soda" — softens skin, leaves it smoothHCO₃⁻415mgP72 national
- Chloridetable-salt anion — coats the skin and holds heat inCl⁻147mgP50 national
- Carbonatestrongly alkaline; slippery feelCO₃²⁻54.1mgP94 national
- Fluoridetrace; drinking limits applyF⁻10.8mgP92 national
- Sulfate"gypsum / Glauber's salt" — vessels and wound healingSO₄²⁻4.0mgP14 national
- Hydrogen sulfidesulfur character — antibacterialHS⁻0.30mgP45 national
- Thiosulfateoxidized sulfurS₂O₃²⁻0.20mgP53 national
- BO2BO₂⁻< —mg
- HSiO3HSiO₃⁻< —mg
- HydroxideOH⁻< —mg
- Metasilicic acidmetasilicic acid — a natural moisturizer for silky skinH₂SiO₃42.2mgP23 national
- Metaboric acidmetaboric acid — mildly antibacterialHBO₂15.7mgP69 national
- Free carbon dioxidefizz — widens blood vessels (strong above 1000 mg/kg)CO₂< —mg
- Free hydrogen sulfide"egg" smell — opens vessels, antibacterialH₂S< —mg
- ArsenicAs< —mg
- CadmiumCd< —mg
- CopperCu< —mg
- Mercurytoxic trace — part of the drinking-safety checkHg< —mg
- LeadPb< —mg
Measured at the source
On the certificate
- Chronic muscle or joint pain and stiffness (rheumatoid arthritis, osteoarthritis, lower back pain, neuralgia, frozen shoulder, bruises, sprains — chronic phase)
- Muscle stiffness associated with motor paralysis
- Reduced gastrointestinal function (heaviness, bloating)
- Mild hypertension
- Impaired glucose tolerance (diabetes)
- Mild hypercholesterolemia
- Mild asthma or emphysema
- Hemorrhoid pain
- Stress-related symptoms (sleep disorders, depressed mood)
- Peripheral circulation disorders
- 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.
- 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.