Standing along the clear stream of the Nakagawa Valley in Nishi-Tanzawa, Shingenkan is known as a hidden hot spring retreat. Its name derives from the legend that approximately 450 years ago, the warlord Takeda Shingen sent his wounded soldiers to bathe and recuperate here after battles against the Hojo clan. The inn's self-sourced alkaline spring water, with a pH exceeding 10, is renowned as a beauty water that softens and smooths the skin, and is also said to be effective for gastrointestinal ailments when consumed as drinking water. The pure Japanese sukiya-style interior features a spacious main bath with scenic views, a panoramic open-air bath, and three private baths, each with a distinctive atmosphere. Guest rooms overlook the Nakagawa stream, offering views of Tanzawa's seasonal beauty, while the inn's rustic country cuisine featuring local mountain and river delicacies is highly praised. Located about 90 minutes from central Tokyo by car, with free shuttle service from JR Yaga Station, it is one of the closest secluded hot springs to the greater Tokyo area.