Nuruyu Onsen Ryokan Nikaido

Ryokan Nikaido is a single isolated inn standing at about 920 meters above sea level on the eastern foot of Azuma-Kofuji in the Azuma mountain range, roughly 18 kilometers west of central Fukushima City. The spring is said to have flowed since the Kyoho era (1716-1736) and has long been famed as a remedy for eye ailments; the inn traces its origin to 1803, when the Nikaido family acquired the rights to the spring and began receiving cure-seeking guests. The present buildings were raised across the Meiji, Taisho and Showa periods, the oldest wing dating to around 1872. Three thatched-roof structures were listed as National Registered Tangible Cultural Properties in 2017, and the inn is a member of the Japan Association of Secluded Hot Spring Inns.

The analysis posted in the bathhouse gives the water as an acidic, iron-bearing aluminium sulfate spring, hypotonic, acidic and low-temperature, with a pH of 2.9 and a source temperature of 31.8 degrees Celsius. This alum-vitriol type water is rare nationwide, and the flow is reported at about 194 liters per minute. Clear and colorless with a faint metallic note, it is poured into the tub entirely unheated, a fully free-flowing supply. Because the temperature sits close to body heat, long soaks are the norm here, and the spring is ranked as the eastern grand champion in Japan's informal ranking of lukewarm springs.

Bathing is limited to separate indoor baths for men and women; there is no open-air bath. Each bathhouse holds a wooden source tub for about six people and a smaller polyethylene tub used for a final rinse, the latter clearly labeled on site as plain hot water rather than hot spring water. Water pours from a single pipe in such volume that it spills over the rim and spreads across the washing floor. Day-trip bathing costs 700 yen for adults and 350 yen for children, from 9:00 to 17:00 with last admission at 16:00. Overnight stays start at 12,800 yen with two meals, and self-catering or long-term cure stays of five nights or more are also available. Heavy snowfall limits the season to late April through late November, with the inn closed in winter.