Akita-Yakeyama Ioutori-no-Yu is a wild hot spring (noyu) located in the fumarolic area on the northwest side of Mt. Akita-Yakeyama (1,366m) in Hachimantai, Kazuno City, Akita Prefecture. Hot spring water naturally gushes at the source of Yunosawa stream, and it was called Ichi-no-Yu during the era of Mataichi Mine that once operated here. The water is strongly acidic sulfur spring with pH 2.2, featuring beautiful milky white water and a strong sulfur smell. While the source temperature is about 65°C, mixing with stream water creates bathing pools at comfortable 42-46°C. A large amount of mineral mud settles at the bottom of the pool, allowing visitors to enjoy a natural mud bath. Access requires about 2 hours of hiking from Goshogake Onsen. There are areas with toxic volcanic gases along the trail, requiring proper hiking equipment and caution. As this is a completely natural hot spring in the wilderness, there are no facilities such as changing rooms or toilets. Mt. Akita-Yakeyama is an active volcano, and bathing is entirely at your own risk.