Sanogawa Onsen

Sanogawa Onsen is a single-inn hot spring tucked into the mountains along the Sanogawa River in Nanbu Town, Minamikoma District, Yamanashi Prefecture, close to the Shizuoka border. The spring was opened in 1974, after locals noticed water with a sulphurous smell flowing into the river. The inn stands alone about 600 metres up a side road from the prefectural highway, surrounded by clear water and forested slopes.

The water is a simple sulphur spring (alkaline, hypotonic, low-temperature), issuing at 30.9C with a pH of 9.6 and a flow rate of 180.5 litres per minute. It carries a faint sulphur aroma and a distinctly silky feel on the skin, sometimes showing a pale green tint. No water is added, no recirculation filter is used, and no chlorine is applied: every tub here is fed directly by the source.

The bathing area consists of separate indoor and open-air baths for men and women, each pairing an unheated source tub with a warmed tub. A 2005 renovation converted the formerly mixed-gender open-air bath into separate facilities. Day bathing runs from 8:30 to 19:30 (last entry 18:30) at 750 yen per adult for one hour, with 60 free parking spaces, a dining room, a rest room and a private bath on site. Overnight stays are also available.