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Akan-Mashū NP, Hokkaido
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Ainu people walked the lakeshore path between Kussharo Kotan and Ikenoyu for generations. At the spring they bathed—and soaked Manchurian elm bark in warm water, softening it into fiber for weaving clothing.
For about 1.2 km, the trail follows the vanished Kushiro Railroad, built in 1887 to move sulfur from Mt. Io. At its peak it carried over 22,000 tonnes a year; grassy embankments still trace the line.
Lake Mashu has no inflowing or outlet rivers, helping keep river-borne particles out. In 1931, its measured transparency reached 41.6 m—a world record at the time. The trail begins at a viewpoint above the lake.
In his 1859 account, explorer Matsuura Takeshiro described 7 houses at Kussharo Kotan. Guided onto the lake by an Ainu local, he wrote a poem about the scenery; a monument near the trail remembers his visit.
Listen for the min-min-zemi on Wakoto Peninsula, which the trail crosses: this cicada survives in eastern Hokkaido only here. Its isolated population is designated a national natural monument.
Wakoto Peninsula began as a volcanic island in Lake Kussharo. Over time, sediment built a natural land bridge to shore, so the trail crosses what was once an island; geothermal heat still warms its soil.
The name Kussharo comes from Ainu *kuccharo*, meaning a lake’s outlet or “throat.” It suits the landscape: Lake Kussharo feeds the Kushiro River, which flows onward through Kushiro Marsh.
At Lake Mashu, fog can spill over the steep caldera rim in a white cascade known as *takigiri*, or “waterfall fog.” It is a rare summer sight, viewed from the trail’s starting area above the lake.
