A simple thermal spring whose alkalinity is the real story: pH 10.3 at the wellhead puts it firmly in strongly alkaline territory, and the water carries the pronounced slippery, soap-like feel that defines Japan's beauty-water family. Mineralization is light — 138 mg/kg of dissolved solids — so the bath is gentle rather than assertive: colorless, clear and tasteless, with only a faint note of hydrogen sulfide detectable at the source. The certificate's spring-type indications are unusually specific for a simple spring, naming autonomic nervous system instability, insomnia and depressed mood alongside the standard list for chronic muscle and joint pain.
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 stage of any illness (especially with fever)
- Active tuberculosis
- Advanced malignant tumor, severe anemia, or other marked physical debilitation
- 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⁺35.5mgP7 national93%
- Calciumsettling and calming; can leave a white mineral bloomCa²⁺2.1mgP7 national6%
- PotassiumK⁺0.30mgP3 national0.6%
- LithiumLi⁺0.10mgP28 national0.6%
- ZincZn²⁺0.01mgP40 national
- Aluminumshows up in acidic volcanic waterAl³⁺< —mg
- BariumBa²⁺< —mg
- Iron (II)rusts brown in air; iron for anemia when drinkableFe²⁺< —mg
- Iron (III)Fe³⁺< —mg
- Magnesiummild; a laxative if you drink itMg²⁺< —mg
- Manganesetrace; companion to iron springsMn²⁺< —mg
- AmmoniumNH₄⁺< —mg
- StrontiumSr²⁺< —mg
- Carbonatestrongly alkaline; slippery feelCO₃²⁻33.1mgP86 national45%
- HSiO3HSiO₃⁻49.0mgP91 national26%
- HydroxideOH⁻4.3mgP98 national10%
- Fluoridetrace; drinking limits applyF⁻3.6mgP69 national8%
- Chloridetable-salt anion — coats the skin and holds heat inCl⁻4.5mgP6 national5%
- Sulfate"gypsum / Glauber's salt" — vessels and wound healingSO₄²⁻5.5mgP16 national5%
- BO2BO₂⁻0.10mgP38 national
- Bromidetrace, sea-originBr⁻< —mg
- Bicarbonate"soda" — softens skin, leaves it smoothHCO₃⁻< —mg
- Hydrogen sulfidesulfur character — antibacterialHS⁻< —mg
- Iodideyellows in air; helps blood lipidsI⁻< —mg
- SS²⁻< —mg
- 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
- ChromiumCr< —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
- Cold sensitivity
- Peripheral circulation disorders
- 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)
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.