A secluded single-inn hot spring located along the Tokawa Valley on the southwestern foot of Mt. Kushigata (elevation 2,052m) in Fujikawa Town, Minamikoma District, Yamanashi Prefecture. A member of the Japan Association of Secluded Hot Spring Inns, the spring is said to have been discovered during Takeda Shingen's gold mining operations in the Sengoku period. The inn has been operating as a hot spring accommodation since around 1887, with over 100 years of history. The water quality is a simple acidic cold mineral spring (iron-containing spring) with a source temperature of 12.6 degrees Celsius and a strongly acidic pH of 2.2. The name Akaishi (red stone) derives from the reddish coloring of the rocks around the spring source. The water is reddish-brown in color, rich in iron content, and is heated before being served to bathers. Inside the building, there is a mixed-bathing large rock bath carved from granite boulders and a women-only indoor bath. On the grounds, there is also a handmade mixed-bathing outdoor bath built by the owner, featuring four pools at different temperatures surrounded by the natural beauty of the valley. Activities include fishing, barbecuing, stargazing from the open-air bath, and peaceful forest walks. The inn has 15 rooms and operates seasonally from late March to late November.