Nigorigo Onsen Asahiso

Asahiso is a hot spring inn at Nigorigo Onsen in Osaka-cho, Gero City, Gifu Prefecture, standing at roughly 1,800 meters on the Hida side of sacred Mt. Ontake, at what climbers call the sixth station. Nigorigo Onsen was developed as a hot spring resort from around 1887 and has long served walkers setting out on the Hida-Osaka trail; unusually for such an altitude, it stays open all year, and nine inns plus a municipal day-bathing facility still stand here. Asahiso opened in 1970, was completely rebuilt in 1994, and belongs to both the Japan Association of Secluded Hot Spring Inns and the Japan Association of Natural Hot Spring Source Inns.

What sets the inn apart is its use of two chemically distinct sources. Its private source, Gensen Asahiso, is a sodium bicarbonate and sulfate spring emerging at 53 degrees Celsius with a pH of 6.72 and a generous yield of 250 liters per minute. The communal source, Nigorigo-no-yu, blended from municipal wells, is a sodium-calcium-magnesium sulfate and bicarbonate spring at 51.9 degrees Celsius and pH 6.3, of which 60 liters per minute is piped to the inn. Neither is diluted, reheated, or chlorinated, and both are served at 100 percent free-flowing strength. The water is faintly cloudy with a metallic scent, and the tubs are kept at 42 to 43 degrees Celsius.

The private source feeds the gender-separated indoor and open-air baths, while the communal source fills a private-use bath that pairs a cypress indoor tub with a rock-built open-air pool large enough for ten people; overnight guests may use it free of charge. Bathing is possible from check-in at 15:00 until 9:30 the next morning. The inn has 12 guest rooms, all with toilets, and geothermal underfloor heating throughout the building drawn from its own spring. Rates start at 27,000 yen per person with two meals, before tax, plus a 150 yen bathing tax and a 200 yen accommodation tax. Day-trip bathing is not offered.