Lake Furen, Coastal lagoon in Nemuro, Japan

Lake Furen stretches across the coastal areas of Nemuro and Betsukai, where saltwater and freshwater mix at sea level. The water body forms a shallow lagoon with natural connections to the surrounding wetlands.

The lake received Ramsar site designation in 2005, gaining international protection for its wetland ecosystems. This recognition became a turning point for safeguarding the region's natural environment.

The name Furen derives from the Ainu "Fure-petsu" (red river), referring to the Furen River, whose water was stained red by marsh runoff; the lake itself was simply called "to" (marsh). On the Shunkunitai sandbar, the Ainu place name "Shunku-nitai" (spruce forest) survives in Japan's only naturally growing Akai spruce grove, alongside one of the country's largest rugosa rose colonies.

Road access is via National Routes 243 and 244 on the north and west shores, Route 44 on the south shore, and Hokkaido Route 475 on the east shore; the Swan 44 Nemuro roadside station sits by the southeast shore. The nature centre on the Shunkunitai sandbar has resident Wild Bird Society of Japan rangers. The lake surface lies at sea level.

The sandbar of Shunkuni-tai is covered by Japan's only naturally growing forest of Glehn's spruce, a species normally found in Sakhalin and the Kurils. The name comes from the Ainu shunku-nitai, meaning 'spruce forest'. The same dunes hold one of Japan's largest colonies of rugosa roses.