The gorge is formed by the erosion of the outer rim of the Towada caldera, a double-layer volcano.
The water level and flow of the Oirase River are regulated by the outflow from Lake Towada, ensuring a stable current year-round.
The forest floor is home to over 300 distinct species of moss, which thrive in the constant humidity of the gorge.
The Choshi Otaki waterfall acts as a natural barrier, historically preventing fish from Lake Towada from swimming downstream into the river.
During the Meiji era, the writer Oomachi Keigetsu played a significant role in popularizing the gorge as a scenic destination.
Oirase Keiryu Gorge is a 14-kilometer mountain stream trail following the Oirase River as it flows from Lake Towada to Yakeyama. The gorge is defined by its series of waterfalls, including the Kumoi, Choshi, and Ashura cascades, which are fed by the lake's consistent water discharge. The walking path runs parallel to the river, crossing through a dense beech, fir, and maple forest. The terrain features moss-covered rocks and geological formations shaped by the river's erosion over millennia. The area serves as a primary drainage point for the Towada-Hachimantai National Park ecosystem. It is accessible via a well-maintained hiking trail that spans the entirety of the river section.
The base of the Ashura-no-nagare current, where the rapids provide the most dynamic water flow against the forest background.
Wear non-slip, waterproof hiking shoes as the riverside paths remain damp and slick even on sunny days.
Bring insect repellent during the summer months, as the humid, forested environment attracts midges and mosquitoes.
Start your hike from the Lake Towada side if you prefer a descent, or from Yakeyama if you prefer an incline.
Attempting to walk the full 14 kilometers in one go without prior fitness preparation; many visitors underestimate the length.
Road access to the gorge is restricted for private vehicles during peak autumn foliage weekends to reduce congestion; use shuttle services during these times.
Stay strictly on the marked path to protect the delicate moss ecosystems and prevent erosion.
