Tousenkyou Onsenkan Toshoka is the premier day-trip hot spring facility in the Kumanokawa Onsen area, situated at the foot of the Sefuri Mountains in Fuji-cho, Saga City, Saga Prefecture. Kumanokawa Onsen is a historic hot spring area said to have been discovered by the Buddhist monk Kukai (Kobo Daishi), and has long been cherished as a therapeutic bathing destination. The facility's most remarkable feature is its radon-rich spring water, gushing from 1,050 meters underground at an exceptional rate of 500 liters per minute, making it one of the most abundant radon springs in Kyushu. The radon content measures 16.4 Mache units, approximately twice the therapeutic spring standard. With a natural source temperature of 43.1 degrees Celsius, the water requires no heating or dilution, enabling a complete free-flowing natural hot spring experience. The water has a pH of 9.34 (alkaline), is colorless, odorless, and tasteless with a soft, gentle feel on the skin. To preserve the volatile radon content, the water is piped from the source to the bath outlets without exposure to air. The main building features gender-separated large baths, outdoor baths, and family baths (3 small, 2 large). The separate HANARE annex offers 6 private family bath rooms with individual rest areas. The spring is reputed to be effective for arteriosclerosis and hypertension, and is also known as a beauty bath.