Aone Onsen Yumoto Fubokaku is a historic hot spring inn with nearly 500 years of history, established in 1528 and located at approximately 500 meters elevation on the eastern slopes of the Zao Mountain Range in Kawasaki Town, Shibata District, Miyagi Prefecture. The inn's name originates from Date Masamune, the founder of the Sendai Domain, who stayed here during the Keicho era (1596-1615) and named it Fubokaku (meaning 'never forget') to commemorate his deeply moving experience. For 21 generations, the Sato family has served as guardians of the hot springs. The water is a simple hot spring (weakly alkaline, pH 7.4, source temperature 49.8-52 degrees Celsius) described as so clear that you can see the tip of a dropped needle. All baths feature 100% natural free-flowing spring water with no dilution, heating, circulation, or disinfection. The inn houses six unique bathing facilities, including the iconic Oyu Kinsen-do which preserves stonework dating to 1546, the Shin-yu bath completed in 1720, and the atmospheric Kura-yu Yokushi set inside a registered tangible cultural property storehouse. Seven buildings within the grounds are designated as National Registered Tangible Cultural Properties. The reconstructed Aone Goten (1932) houses artifacts and documents from the Date clan. A member of the Japan Association of Secluded Hot Spring Inns. Day-trip bathing is not available, maintaining an exclusive environment for overnight guests only.