Lake Ushiku, Freshwater lake in Ryugasaki, Japan

Lake Ushiku is a shallow freshwater lake in Ryugasaki, Ibaraki Prefecture, with a perimeter of about 25.5 km, an average depth of about 1 m and a maximum of roughly 3 m. It lies in the Kokaigawa lowland at the edge of the Tsukuba-Inashiki plateau. The Yata River and the Egawa drain it, while the Negoya, Inari, Higashiyata, Nishiyata and Toyama rivers flow in.

The lake was formerly called Ōta-numa and lies entirely within Ryugasaki, though it shares its name with neighbouring Ushiku. Its name is linked to a legend told at Kinryū-ji of a lazy novice who turned into a bull and drowned; the abbot kept the severed tail as a hossu, still a temple treasure. The painter Ogawa Gyosen, who lived on the north shore, drew many kappa pictures there.

The name is linked to a legend told at Kinryū-ji: a lazy novice who skipped prayers turned into an ox, and his tail, cut off as the abbot tried to pull him from the water, was made into a fly whisk kept at the temple. The lakeside path is named Ushiku-numa Kappa no Komichi after kappa legends, and the painter Ogawa Uisen, who lived on the north shore, left many kappa paintings.

The lake is accessible for boating, fishing, and bird watching, with marked walking paths running around the shoreline for easy exploration. Best visited during mild weather when the pathways are most comfortable to navigate.

The lake is linked to the legend of a lazy temple boy at Kinryū-ji who turned into an ox and sank in the water; the abbot kept the severed tail as a hossu, still a temple treasure. The lakeside path is named Ushiku-numa Kappa no Komichi after its kappa legends, and painter Ogawa Usen, who lived on the north shore, left many kappa paintings.