Tazawa Onsen, located at the foot of Mt. Jukkan in Aoki Village, Chiisagata District, Nagano Prefecture, is an ancient hot spring with approximately 1,300 years of history, said to have been discovered by the ascetic En no Gyoja during the Asuka period. The public bathhouse 'Uchinyu' derives its name from a legend that a mountain witch bathed here and gave birth to Sakata Kintoki (Kintaro, the Golden Boy), earning it the reputation as a 'fertility spring.' The building was rebuilt in wood in 2000 and features a charming traditional atmosphere with an attached foot bath. The water is an alkaline simple sulfur spring with a pH of 9.3-9.53. The source temperature is 38.5-40.2 degrees Celsius, providing a pleasantly warm bath. With an abundant flow of 450 liters per minute, the water is delivered as a completely natural free-flowing source with no dilution, heating, circulation filtration, or disinfection. The clear, colorless water with a faint sulfur scent is known for the fine bubbles that cling to the skin during bathing, making it popular as a beauty spring. The area has connections to the renowned author Toson Shimazaki and is designated as a National Health Resort Hot Spring by the Ministry of the Environment. At just 200 yen for adults, this beloved spring attracts both locals and tourists alike.