A lightly mineralized alkaline simple thermal spring (dissolved solids only 183 mg/kg). At pH 9.2 it sits firmly in Japan's beauty-water family, with the slippery soft feel that high alkalinity gives. The wellhead reading is 38 degrees Celsius and the cert classifies it as hypotonic, alkaline and warm-class — a gentle, low-stimulation 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
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⁺41.8mgP10 national
- Calciumsettling and calming; can leave a white mineral bloomCa²⁺7.0mgP20 national
- Potassiumminor; matters for drinking limitsK⁺0.92mgP11 national
- Aluminumshows up in acidic volcanic waterAl³⁺< —mg
- CopperCu²⁺< —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
- Chloridetable-salt anion — coats the skin and holds heat inCl⁻44.2mgP25 national
- HydroxideOH⁻13.1mgP100 national
- Bicarbonate"soda" — softens skin, leaves it smoothHCO₃⁻8.9mgP5 national
- Carbonatestrongly alkaline; slippery feelCO₃²⁻0.30mgP14 national
- Bromidetrace, sea-originBr⁻0.05mgP7 national
- Thiosulfateoxidized sulfurS₂O₃²⁻0.03mgP31 national
- AsO2AsO₂⁻< —mg
- Iodideyellows in air; helps blood lipidsI⁻< —mg
- Metasilicic acidmetasilicic acid — a natural moisturizer for silky skinH₂SiO₃32.7mgP15 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.
- 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.