Uchinomaki Onsen, Aso, Kumamoto
Sozankyo Inn
Best for a short, carefully timed soak if you value a historic inn and clearly documented source-flowing water. Day-use bathing is limited to 13:00–15:00, and the inn asks visitors to check ahead on busy dates. Private baths and evening bathing should not be assumed to be part of the day-use offer.
Facility photos
Check before bathing
- Opening hours
- 13:00–15:00. Adult admission ¥700; children ¥300; preschool children ¥200. Confirm ahead on busy dates and before holidays.
Spring & water temperature
- Spring-source temperature
- 48.5°C on the operator's spring analysis; another section of the same site gives 43.5°C. The discrepancy is unresolved.
- Bathing temperature
- Not published. The operator's reference to about 40°C at an outlet is not a measured pool temperature.
- Spring source
- Sozankyo's own spring.
- Spring classification
- Neutral sodium-magnesium-calcium sulfate spring; hypotonic and high-temperature.
- pH
- A neutral classification is given, but no numeric pH is published.
- Flow rate
- 273.3 L/min on the operator's spring analysis.
- Water handling
- The operator specifies no heating, no added water, source-flowing supply, no recirculation and a complete daily drain and cleaning.
The day-use window is short and busy dates may require confirmation.
How to read a bath profile
Spring-source temperature and actual bathing temperature are kept separate. Each score is shown independently for comparison rather than collapsed into one overall score.
