Lake Shumarinai is a dam lake created in conjunction with the construction of Uryu Dam, and is the largest man-made lake in Japan, with a surface area roughly the size of 30 Tokyo Disneylands. The Lake Shumarinai area was designated a prefectural natural park in 1974 (Showa 49), and is home to a vast expanse of virgin land that is subject to strict regulations for nature conservation, and still retains its original natural form.

The lake, which is home to 13 islands of various sizes, changes its appearance with each season. The intricate topography, reminiscent of a Nordic fjord, nurtures lake creatures and deep virgin forests, and the lake, surrounded by such deep nature, is known as a mysterious lake, home to the Japanese huchen, Japan's largest freshwater fish, known as a mystical fish. During trout season, anglers from within and outside Hokkaido, and sometimes even from overseas, visit the lake, and in winter, it becomes a popular spot for smelt fishing.

During the summer camping season, many campers visit the area. As it is not a tourist destination, it is popular with experienced campers and motorcyclists, and one of its features is that it has many repeat visitors as a place where they can relax and spend their time on their own.