A historic hot spring inn located on the middle slopes of the Ou Mountains along the Toyosawa River in Hanamaki City, Iwate Prefecture. The hot spring was discovered approximately 600 years ago, and the ryokan was established in 1786, boasting over 230 years of history. The origin story tells of a white monkey healing its wounds in the spring, giving rise to the legend behind the name. This is the only ryokan mentioned in Kenji Miyazawa's fairy tale 'The Bears of Nametoko Mountain,' and Miyazawa frequently visited since childhood. The signature feature of Fujisan Ryokan is 'Hakuen no Yu' (White Monkey Bath), Japan's deepest rock bath with an average depth of 125cm, requiring bathers to stand while soaking. Hot spring water naturally wells up from the bottom of the hand-carved rock bathtub, creating a unique bathing experience where water pressure envelops the entire body. The bath was progressively dug deeper whenever water flow weakened, reaching its current depth. Digging any deeper would allow river water from the nearby Toyosawa River to mix in, making this the maximum possible depth. The bath features a three-story atrium structure with an overwhelming sense of openness. The ryokan has 5 different hot spring sources, and all 4 bathing areas offer 100% pure natural flowing spring water without any heating or water addition. In addition to Hakuen no Yu, there are gender-separated indoor and outdoor baths 'Katsura no Yu,' a panoramic semi-open-air bath overlooking a waterfall 'Shiraito no Yu,' and 'Gin no Yu' which alternates between private family bath, men's bath, and women's bath depending on time. The ryokan has been selected as one of 'New Japan's 100 Famous Hot Springs' and 'Japan's Hot Spring Heritage,' receiving high acclaim from hot spring enthusiasts nationwide. The wooden building constructed with zelkova timber evokes a retro atmosphere reminiscent of the bathhouse in Hayao Miyazaki's 'Spirited Away.' In 2024, a 'Nametoko-yama Sauna' themed after Miyazawa Kenji's 'The Bears of Nametoko Mountain' opened, allowing guests to enjoy both hot springs and sauna.