A gentle simple thermal spring, lightly mineralized at about 985 mg/kg of dissolved solids. It emerges hot at 52.3 °C and is weakly alkaline at pH 8.3, giving the soft, slippery feel of the Japanese beauty-water family. A generous 175 mg/kg of metasilicic acid leaves a thin silica film that makes skin feel noticeably smoother.
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⁺179mgP46 national71%
- AmmoniumNH₄⁺1.3mgP70 national10%
- Potassiumminor; matters for drinking limitsK⁺32.1mgP76 national7%
- LithiumLi⁺—mg0.4%
- Calciumsettling and calming; can leave a white mineral bloomCa²⁺24.4mgP42 national
- Bicarbonate"soda" — softens skin, leaves it smoothHCO₃⁻337mgP67 national50%
- Chloridetable-salt anion — coats the skin and holds heat inCl⁻92.7mgP39 national24%
- Sulfate"gypsum / Glauber's salt" — vessels and wound healingSO₄²⁻104mgP55 national20%
- Carbonatestrongly alkaline; slippery feelCO₃²⁻20.4mgP68 national6%
- Metasilicic acidmetasilicic acid — a natural moisturizer for silky skinH₂SiO₃175mgP78 national
- Metaboric acidmetaboric acid — mildly antibacterialHBO₂4.3mgP32 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.