Dokusawa Kosen Kaminoyu

Kaminoyu is a lone mountain inn in the Yashiro district of Shimosuwa Town, Suwa District, Nagano Prefecture, and a member of the Association for Preserving Japan's Secluded Hot Springs. Local lore says Takeda Shingen used the Dokusawa mineral spring to treat people injured in gold mining, and in 1937 the water was licensed as a natural mineral spring medicine. It is close to Suwa Taisha shrine, surrounded by cedar and cypress trees.

The water is an iron (II)-aluminum-sulfate cold mineral spring (acidic, hypotonic) with a strongly acidic pH of 2.5 and a sour, lemon-like taste. Fresh from the ground it is clear and colorless, but once heated and exposed to air the iron oxidizes and turns the bath orange. The main tub is heated and circulated without chlorine disinfection, while a small neighboring tub holds unheated source water that flows freely, so bathers can alternate between hot and cold.

There is one indoor bath each for men and women, with no open-air bath or sauna. Day-use bathing costs 1,000 yen for adults and 500 yen for children aged 3 to elementary school, from about 10:00 to 14:00, with irregular closing days. The inn has 14 Japanese-style rooms across its main, new and old buildings and serves mountain cuisine with river fish and wild vegetables.