Kobayashi Onsen Cosmos Onsen

Cosmos Onsen is a day-use bathhouse standing among the rice fields of Nanseikata in Kobayashi City, Miyazaki Prefecture, with Mount Hinamori of the Kirishima range rising in view. Officially operated as the Kobayashi Onsen Fureai Exchange Center, it shares its building with an adjoining day-service facility for the elderly. The source is registered as Kobayashi Onsen, though locals have always called the place Cosmos Onsen. It is one of the certified stops on the Kyushu Onsen Do, the eighty-eight hot spring pilgrimage of Kyushu, which brings in enthusiasts from well beyond the prefecture.

The water is classified as a sodium-magnesium-calcium bicarbonate-sulfate-chloride spring, hypotonic, neutral and hot. It emerges at 47.7C with a pH of 6.7 and a total mineral content of 3.146 g/kg, pumped from a wellhead about three kilometres away at 60 litres per minute. The bath water is nearly colourless with a faint white cloudiness, and thick cream to dark brown mineral deposits coat the spouts and tub rims. There is no heating and no recirculation, though the medium-temperature tub is tempered with cold water and sodium hypochlorite is used for disinfection.

The bathhouse is a plain wooden room with the atmosphere of a rural community bath. A single indoor pool is divided in two: the hotter side, fed straight from the source, sits around 45C, while the tempered side runs 42 to 43C. A cold plunge stands at the front, and regulars alternate between the two. There is no open-air bath and no sauna. Admission is 500 yen for adults, 300 yen for elementary and junior high students and 200 yen for preschoolers, with under-threes free. Hours are 10:00 to 21:00, closed Thursdays, and no overnight stays are offered.