Kamiyu Onsen Kawara no Yu is a natural open-air hot spring nestled deep in the mountain gorges of Totsukawa Village in Yoshino District, Nara Prefecture, renowned as one of the Kansai region's most secluded hidden hot springs. Its origins trace back to the Kyoho era (1716-1736), when local villagers discovered hot water gushing from the riverbank of the Kamiyu River, giving it approximately 300 years of history. Among the three hot springs comprising the Totsukawa Onsen Village (Yusenchi, Totsukawa, and Kamiyu), it occupies the most remote location, enveloped in the tranquility of pristine wilderness. The spring water is classified as a sulfur-containing sodium bicarbonate spring with a mildly alkaline pH of 8.3. With a source temperature of 76.6 degrees Celsius and a generous flow rate of 124 liters per minute, the water is served as 100% free-flowing source water under the village's pioneering 2004 'Source Water Free-Flow Declaration,' with no heating, circulation, or chlorine disinfection (20% cold water added in summer months). Though colorless and transparent, the water contains abundant white mineral deposits (yu no hana) and carries a faint hydrogen sulfide aroma. The sodium bicarbonate content softens skin, earning it the reputation as a 'beauty bath.' The men's bath is a fully open-air rotenburo set directly beside the mountain stream, while the women's bath is a semi-enclosed concrete-walled outdoor bath. The facility was destroyed by the devastating Kii Peninsula floods in 2011, but was magnificently restored in 2017 under the management of the nearby Kamiyuso inn. It is certified as Pure Onsen Grade A by the Pure Hot Spring Association.