Hiuchi no Yu is a public day-trip hot spring facility located in Hinoemata Village, Minamiaizu District, Fukushima Prefecture, at an elevation of approximately 920 meters. Hinoemata Village is known as the municipality with the lowest population density in Japan, serving as the Fukushima-side gateway to Oze National Park. This secluded mountain village preserves legends of Heike clan refugees and a 270-year-old Kabuki tradition. Hinoemata Onsen was successfully drilled in 1972, and the village is blessed with such abundant hot spring water that it is supplied to every household. Hiuchi no Yu is a village-operated public bathhouse situated on a hill overlooking the Funaki River. Its source is Hinoemata Onsen No. 5, classified as a simple sulfur spring with an alkaline pH of 9.1. The water flows freely from the source at 62.4 degrees Celsius with no dilution, heating, or chlorine treatment. The facility features a bright cypress-scented indoor bath and an outdoor rock bath surrounded by natural beech and zelkova trees, offering views of the Funaki River from the open-air tub. The water is colorless and transparent with a faint sulfur scent and a slightly silky texture. It is especially popular among hikers returning from Ozegahara, Mt. Hiuchigatake, and Mt. Aizu-Komagatake.