Kamiyama Onsen is a historic hot spring located in Kamiyama Town, Myozai District, Tokushima Prefecture, with a legend that a celestial maiden bestowed this sacred spring upon the land. Founded in 1868 (Keio 4) as a communal bathhouse operated by local residents, it served laborers from the nearby Jiro Copper Mine and attracted visitors from afar who heard of its exceptional water quality. After a temporary closure in 1875 due to the mine''s decline, a Buddhist priest of Zenkakuji Temple confirmed the spring''s medicinal value, and it reopened in 1925 as Benten Kosen-yu. In 1972 it was reestablished as the Kamiyama Onsen Recuperation Center, Hotel Shikinosato was added in 1993, and the day-trip bathing facility Iyashi-no-Yu opened in 2003. The locals enshrined the celestial maiden as Shiomizu Daimyojin, and her small shrine still stands near the spring source today.

The spring water is classified as a sodium chloride and sodium bicarbonate spring (hypotonic, mildly alkaline, cold mineral spring) with a pH of 8.2. The source temperature is just 5.4 degrees Celsius, and the dissolved mineral content reaches 2,767.2 mg/kg. The distinctive bicarbonate-rich saline water has a slightly silky texture that leaves the skin remarkably smooth, earning it the reputation as a bijin-no-yu (beauty spring). Despite its high salt content, the water feels refreshingly clean and retains warmth long after bathing.

Iyashi-no-Yu features two themed bathrooms that alternate weekly between men and women: Aoishi-no-Yu with classical design using locally quarried blue stone, and Tamaishi-no-Yu with walls adorned with round river stones. The tatami-floored bathing area provides a soft, slip-resistant surface for comfortable walking. Facilities include a main bath with bubble jets, a semi-open-air bath, sauna, cold plunge, waterfall shower, reclining bath, and children''s bath, with a total capacity of 200 bathers. Day-trip admission is 680 yen for adults and 340 yen for children. Hotel Shikinosato also operates as an accommodation facility, and Restaurant Kawasemi serves creative Japanese cuisine courses.