The Japanese white crucian carp, also known as Japanese carp, white crucian carp, or gengoro-buna, is a species of freshwater fish in the carp family. It is found in Japan and, as an introduced species, in several other countries in Asia. This fish is closely related to the commonly known goldfish.

Lake Biwa is the largest freshwater lake in Japan. It is located entirely within Shiga Prefecture, northeast of the former capital city of Kyoto. Lake Biwa is an ancient lake, over 4 million years old. It is estimated to be the 13th oldest lake in the world. Because of its proximity to Kyoto, references to Lake Biwa appear frequently in Japanese literature, particularly in poetry and in historical accounts of battles.