Tradition has it that, when a battle occurred between the Minamoto and Taira clans in the late Heian period, the dead body of Taira no Noritsune's wife was washed up on the shore of Otsumi in present-day Moji-ku, and buried by local people, who later erected a monument. It is believed that, at this battle, many defeated samurai of the Taira clan sank deep into the sea, and became mask crabs (called "Taira clan crabs"), while killed court ladies were incarnated as kappa, that is, water imps. Amagoze is the leader of these kappa. Legends about these kappa still live on, including one about these kappa putting the offspring of the Minamoto clan to trouble by appearing in ponds and rivers in various places in the spring.