Kaifu River is a 36-kilometer-long river that flows through Kaiyoucho, in Kaifu District, Tokushima Prefecture. It is a good representative of limpid water in Japan. The river is wider up stream. Also, the trees are evergreen; therefore the mountains appear to be green, even in winter. There are no dams. Rare fish that breed in the river estuary include the Lates japonicus, Anguilla marmorata, and others. Cherry trees have been planted along the banks. Furthermore, the waterfall located 2km up the Karei valley has been designated as one of  the 100 major waterfalls in Japan. Kaifu River is famous for its water quality. In 1991, Sanae Ikeda, a professor of Tokushima University compared the water quality of Shimanto River (checked at points between upstream 40KM) and Kaifu River (checked at points between upstream 36.3KM) and came up with the result that Kaifu River was far cleaner. Many people visit this river to pursue the thrill of Kaifu fishing. The vicinity of the estuary area is full of nature and invokes unspoilt scenery of the past, so that people can soak in nostalgia.