Betsu-shi Onsen ~ Tenkū no Yu ~
- Location
- Iyo, Ehime, Japan
- Water type
- sodium chloride
- Temperature
- 41 °C
- pH
- 7.3
Water profile
Relaxing — deep, immediate muscle release.
Loaded with major ions — the essential minerals (Ca, Mg).
Dense, salty water — you float without effort.
On the western coast of Shikoku, overlooking the Seto Inland Sea, Betsu-shi Onsen — whose name evokes a heavenly or sky-open bath — belongs to the thermal tradition of Iyo in Ehime Prefecture. The tectonic subduction beneath Shikoku feeds a network of sodium-chloride springs that have nourished the island's bathing culture across centuries.
The sodium-chloride water, at around 41 °C, is noted for its lasting warming effect and the soft, smooth sensation it leaves on the skin. The Tenkū no Yu concept — bath of the heavens — suggests an open-air setting that invites contemplation of the Inland Sea and its scattered islands, especially when the sky turns orange at dusk.
Iyo and its surroundings retain an authentically Japanese character, well away from the most-travelled circuits. The historic coastal ports, the 88-temple Shikoku Pilgrimage, and the onsen together form a triad of experiences that belong to the very essence of the island — culture, nature, and warm water interwoven in quiet harmony.