An ultimate wild hot spring located in the northwest part of Mount Akita Yakeyama at the source of Yu-no-sawa in the lowest part of the fumarole zone, Kazuno City, Akita Prefecture. A secret hot spring in the wilderness accessible only via mountain trails, praised among wild hot spring enthusiasts as 'would rank high in a national popularity vote.'

Spring quality is acidic, with numerous hot spring pools along the valley, temperature increasing upstream to around 40°C. Characterized by transparent bluish-white hot spring water flowing abundantly, fresh and pure. Abundant water volume with many bathing spots.

Access starts from Goshogake Onsen parking lot, via mountain trail through Beko-Yachi wetland to Yu-no-sawa, then to the wild hot spring (Ioutori-no-yu), past mining ruins, through narrow ridge at Soranuma to Yakeyama Shelter. Previously restricted due to eruptions and toxic gas at Soranuma, but restrictions recently lifted with ropes installed for easier passage.

Bathing in open, magnificent scenery is exceptional, with top-level water quality, volume, and views among wild hot springs.

【Important Precautions】

・Wild hot spring with no managed facilities, enter at own risk

・Via mountain trail, mountaineering equipment required

・Bear habitat - bear bells and bear spray essential

・Weather assessment and climbing plan required

・Avoid solo activity

・No facilities, changing rooms, or toilets