Yokomuki Onsen

Yokomuki Onsen in Inawashiro Town, Fukushima Prefecture holds the historical distinction of being said to be the first location in Fukushima Prefecture where therapeutic bathing — toji — was practiced, a claim that underscores its foundational importance in the prefectural onsen tradition and connects it to the ancient Japanese practice of extended therapeutic stays at volcanic mineral springs for the treatment of chronic illness. The spring complex is divided into three bathing areas — the upper Kami no Yu, the middle Naka no Yu, and the lower Shimo no Yu — each with distinct management and character, while the Shimo no Yu operated by Takinoya features the exceptional geological phenomenon of thermal water welling directly from the floor of the bathing pool, a spring-bottom emergence that has been identified by onsen critics as a prime example of Japan's most intimate geothermal bathing configurations. Yokomuki Onsen's historical primacy within Fukushima's therapeutic bathing tradition, its three-tiered spring structure, and the geological rarity of its floor-welling lower bath make it a destination of exceptional cultural and scientific interest within the volcanic heritage of the former Aizu domain.