A strongly alkaline simple thermal water reaching pH 10.5 — high enough to give the slippery, soft feel of Japan's beauty-water family. It is only lightly mineralized at 181 mg/kg dissolved solids, but a generous ~80 mg/kg of metasilicic acid leaves the kind of thin silica film that makes skin feel noticeably smoother afterwards.
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
- acute phase of illness
- active tuberculosis
- severe heart 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.
- Calciumsettling and calming; can leave a white mineral bloomCa²⁺4.1mgP15 national9%
- Sodiumsalt's cation — pairs with chloride to make the water saltyNa⁺47.9mgP13 national
- Potassiumminor; matters for drinking limitsK⁺0.10mgP1 national
- HSiO3HSiO₃⁻11.8mgP62 national16%
- Fluoridetrace; drinking limits applyF⁻1.0mgP47 national
- Metasilicic acidmetasilicic acid — a natural moisturizer for silky skinH₂SiO₃79.9mgP47 national
Measured at the source
On the certificate
- stress-related symptoms
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.