The river boy is a legendary creature in Japanese mythology. It has a bird's beak, frog's limbs, monkey's body and tortoise's shell, just like a synthesis of many animals. Legend has it that its weakness is the plate above its head. As long as he is tricked into bending over and letting the water flow from the plate above his head, he will lose all his energy. Legend has it that the "river boy" lives in rivers or ponds all over Japan. According to the research data of folklore scholar Junichiro Ishikawa, the legend of river children is widely distributed, including Northeast Japan, Central Japan, Feng Jingen, Toyama Prefecture in Ishikawa, Shikoku, Kitakyushu Island and Saga in Kyushu Island.
Miyazaki Prefecture, Amami Islands and Okinawa Prefecture have different appellations for river children according to different dialects. * * * Tongdian is called "Kappa" because it is a "child living in a river". It turns out that the river boy is an elf in the water and is regarded as a river god worshipped by people. There is also a saying that the river boy is the messenger of the water god, which is transformed from the frost falling from the water god.