Uses natural hot spring water
A gentle simple thermal spring — hot at 45.6 °C, with neutral pH and hypotonic mineralization, served as free-flow source water (kakenagashi). With little chemical bite, it relies on heat and water volume rather than mineral punch, and the posted indications list the usual constellation of nerve pain, muscle ache, joint stiffness, and post-illness recovery.
Analyzed Jun 26, 1998·和歌山県衛生公害研究センター
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679. Senjonoyu Hot Spring, Shirahama, Wakayama ★ Onsen for 850. Operating hours are 13:00-21:00 (except Mon and Tue). Can only roughly verify internet photos - visited in the evening, but the baths themselves match the photos. Small outdoor stone bath. In the evening you can only see nearby buildings while standing, but during the day the ocean should be visible. Sitting in the bath the view is mostly rocks, nearby trees, and sky. Clear water, temperature around 39. Indoor bath with clear water, temperature around 41. Breathing inside is comfortable. Solid cozy place, worth considering for a visit. 09.11.2025
