Takaraso is a secluded hot spring inn located at approximately 600-700m elevation in the Kazuma district, the innermost area of Hinohara Village in Tokyo's Nishitama region, facing the headwaters of the Minami Akigawa River. The inn's 300-year-old kabuto-zukuri (helmet-style) building was designated as a Registered Tangible Cultural Property on March 29, 2013, and serves as a precious example of vernacular architecture that conveys the history of sericulture in the region. The building faces north along an old mountain road, features a hipped cypress bark thatched roof, and exhibits a distinctive Fuji-style double kabuto-zukuri form on its east gable side, earning high cultural recognition as a large-scale folk house that preserves regional history and the transition of sericulture practices. This rare hot spring, mentioned in the Musashino Fudoki (historical records), is one of the few remaining hot springs in the Tama area. According to legend, the name Janoyu (Snake Hot Spring) originates from a tale of an injured serpent healing its wounds in the spring waters by the riverbed. As Tokyo's only member facility of the Japan Secret Hot Springs Protection Association, it continues to share the charm of secluded hot springs with modern visitors. The spring water is classified as alkaline simple sulfur cold mineral spring (hypotonic, alkaline, cold spring), with a source temperature of 10.4-10.5°C and remarkably high alkalinity of pH 10.0-10.5. The water is heated for bathing and offers gentle bathing comfort with a distinctive sulfur aroma. The inn features two indoor baths with large windows overlooking forest scenery, creating a sense of unity with nature. A tatami mat rest area is also available. The cuisine features handmade mountain village dishes, with seasonal mountain vegetables, mushroom dishes, and homemade three-year-aged miso showcasing local ingredients in simple yet profound flavors that have earned popularity among guests. The two-story wooden inn contains five guest rooms, surrounded by the gentle sounds of the Minami Akigawa River's stream in a tranquil environment where guests can forget urban bustle and relax completely. Serving as an ideal base for exploring Hinohara Village's abundant nature, waterfall tours (Ryujin Falls, Kuzuryu Falls, etc.), Tomin no Mori (Tokyo Metropolitan Forest), and Mount Mitou hiking, this inn offers a unique experience of enjoying a secret hot spring, traditional architecture, and mountain village cuisine all while staying in Tokyo.