Kumanokawa Onsen Motoyu Kumanokawa Bathhouse

This public bathhouse is the original source bath, or motoyu, of Kumanokawa Onsen, which rises along the Kase River in the Sefuri Mountains north of Saga City. Legend holds that the spring was discovered in 816, when the monk Kobo Daishi watched a plover with a broken leg wade in and out of a warm pool in a rice paddy until it healed and flew away. Kumanokawa was already well known by the late Sengoku period, as a letter from Nabeshima Katsushige, the first lord of the Saga domain, mentions taking the cure here, and a village headman revived the buried spring during the Enpo era (1673-1681). In 1966 it was designated a National Health Resort Hot Spring together with neighboring Furuyu Onsen, a designation lifted in 2019.

The source, named Kumanokawa-so Gensen, is an alkaline simple weak radioactive spring emerging at 29.4 degrees Celsius with a pH of 9.55. Long noted for having one of the highest radon contents in Kyushu, the water is clear and odorless yet clings softly to the skin, and bathers commonly report a smooth, silky feeling afterward. No water is added, and there is no recirculation or chlorination; the coolest tub receives the source water exactly as it emerges.

The bathhouse has only indoor baths, separated by gender, with no open-air bath, sauna, or private bath. Three tubs of differing temperature stand side by side: two heated to roughly 40 and 35 degrees, and one unheated at about 30 degrees, allowing very long soaks by moving between them. Hours are 9:00 to 20:30, closed Tuesdays and Fridays. Admission is 700 yen for adults, dropping to 500 yen after 15:00 and 300 yen after 17:00, and a single payment covers the whole day. The facility is for day-trip bathing only and does not offer lodging.