A simple thermal spring blended from two sources (Kawachi No.5 and Kanaya Onsen). Hypotonic and weakly alkaline, it has a soft, gentle feel on the skin and sits in the Japanese beauty-water family. The wellhead runs lukewarm at 36.2 °C, so it is reheated for bathing; with no dilution, recirculation, or disinfection, it stays an undemanding, lightly mineralized soak.
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
Take care
- Active phase of illness (especially when feverish)
- Active tuberculosis
- Advanced malignant tumors or severe anemia and other cases of marked physical debilitation
- Serious heart or lung disease, such as becoming short of breath on slight exertion
- Severe kidney disease accompanied by edema
- Gastrointestinal bleeding
- When there is visible bleeding
- Acute illness, or the acute exacerbation phase of a chronic disease
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⁺54.2mgP15 national
- Calciumsettling and calming; can leave a white mineral bloomCa²⁺16.7mgP36 national
- Potassiumminor; matters for drinking limitsK⁺3.6mgP30 national
- Magnesiummild; a laxative if you drink itMg²⁺0.40mgP19 national
- Bicarbonate"soda" — softens skin, leaves it smoothHCO₃⁻71.2mgP34 national
- Sulfate"gypsum / Glauber's salt" — vessels and wound healingSO₄²⁻58.5mgP46 national
- Chloridetable-salt anion — coats the skin and holds heat inCl⁻30.0mgP22 national
- Carbonatestrongly alkaline; slippery feelCO₃²⁻1.2mgP20 national
- Fluoridetrace; drinking limits applyF⁻0.40mgP33 national
- HydroxideOH⁻0.0070mgP23 national
- Metasilicic acidmetasilicic acid — a natural moisturizer for silky skinH₂SiO₃47.5mgP28 national
- Metaboric acidmetaboric acid — mildly antibacterialHBO₂0.20mgP6 national
- Metaarsenious acidHAsO₂0.0090mgP31 national
- CadmiumCd< —mg
- CopperCu< —mg
- Mercurytoxic trace — part of the drinking-safety checkHg< —mg
- LeadPb< —mg
Measured at the source
On the certificate
- Chronic pain or stiffness of muscles or joints (rheumatoid arthritis, osteoarthritis, lower back pain, neuralgia, frozen shoulder, bruises, sprains in the chronic phase)
- Muscle stiffness associated with motor paralysis
- Sensitivity to cold
- Peripheral circulatory disturbance
- Reduced gastrointestinal function (heaviness in the stomach, intestinal gas, etc.)
- Mild hypertension
- Impaired glucose tolerance (diabetes)
- Mild hypercholesterolemia
- Mild asthma or emphysema
- Hemorrhoid pain
- Various stress-related symptoms (sleep disorders, depressive states, etc.)
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.