A gentle alkaline simple thermal spring, blended from some thirty wells across the Izunagaoka district. At pH 9.3 it is strongly alkaline, giving the slippery feel of the Japanese beauty-water family, while the dissolved-solids total of just 0.63 g/kg keeps the water light on the body. The wellhead runs at 62.5 °C, placing it among Japan's hotter natural sources.
Good for
Aches & joints
Warmth eases stiffness and raises the pain threshold. Radon and sulfate springs show the strongest evidence for joint and muscle pain.
stiff shoulders
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⁺177mgP46 national87%
- Calciumsettling and calming; can leave a white mineral bloomCa²⁺20.9mgP40 national12%
- PotassiumK⁺0.30mgP3 national0.9%
- Iron (II)Fe²⁺0.10mgP30 national0.0%
- Aluminumshows up in acidic volcanic waterAl³⁺< —mg
- CopperCu²⁺< —mg
- Iron (III)Fe³⁺< —mg
- Magnesiummild; a laxative if you drink itMg²⁺< —mg
- Manganesetrace; companion to iron springsMn²⁺< —mg
- Chloridetable-salt anion — coats the skin and holds heat inCl⁻142mgP47 national45%
- Sulfate"gypsum / Glauber's salt" — vessels and wound healingSO₄²⁻181mgP63 national43%
- Carbonatestrongly alkaline; slippery feelCO₃²⁻18.8mgP66 national7%
- Bicarbonate"soda" — softens skin, leaves it smoothHCO₃⁻16.9mgP11 national3%
- BO2BO₂⁻6.0mgP86 national2%
- HydroxideOH⁻0.30mgP74 national0.2%
- AsO2AsO₂⁻0.20mgP87 national
- Hydrogen phosphateHPO₄²⁻0.10mgP34 national
- Bromidetrace, sea-originBr⁻< —mg
- Hydrogen sulfidesulfur character — antibacterialHS⁻< —mg
- Iodideyellows in air; helps blood lipidsI⁻< —mg
- Thiosulfateoxidized sulfurS₂O₃²⁻< —mg
- Metasilicic acidmetasilicic acid — a natural moisturizer for silky skinH₂SiO₃65.0mgP41 national
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.
- Donaubauer AJ et al. Serial radon spa therapy on pain in musculoskeletal disorders. Frontiers in Immunology, 2024.
- Verhagen AP et al. Balneotherapy for rheumatoid arthritis. Cochrane Database of Systematic Reviews CD000518, 2015.
- 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.