A lightly mineralized simple thermal spring. The wellhead measures 29.7 °C, putting it in the low-temperature class — the bath water is reheated before serving. Neutral pH (7.4) and a faint yellow tint give a gentle, unassuming character, while a meaningful 60.8 mg/kg of metasilicic acid leaves the skin slightly smoother than the modest mineralization would suggest.
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⁺32.5mgP7 national61%
- Calciumsettling and calming; can leave a white mineral bloomCa²⁺13.4mgP30 national29%
- Magnesiummild; a laxative if you drink itMg²⁺2.0mgP35 national7%
- Potassiumminor; matters for drinking limitsK⁺1.9mgP22 national2%
- Iron (II)Fe²⁺0.60mgP56 national0.9%
- Aluminumshows up in acidic volcanic waterAl³⁺< —mg
- Manganesetrace; companion to iron springsMn²⁺< —mg
- Bicarbonate"soda" — softens skin, leaves it smoothHCO₃⁻136mgP48 national93%
- Chloridetable-salt anion — coats the skin and holds heat inCl⁻4.9mgP7 national6%
- Sulfate"gypsum / Glauber's salt" — vessels and wound healingSO₄²⁻1.6mgP9 national1%
- Metasilicic acidmetasilicic acid — a natural moisturizer for silky skinH₂SiO₃60.8mgP37 national
- Metaboric acidmetaboric acid — mildly antibacterialHBO₂0.20mgP6 national
- Free carbon dioxidefizz — widens blood vessels (strong above 1000 mg/kg)CO₂4.4mgP29 national
- Free hydrogen sulfide"egg" smell — opens vessels, antibacterialH₂S0.10mgP61 national
- ArsenicAs< —mg
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.