Emperor Nintoku
The ancient chronicle "Nihongi" contains references to "mizuchi". Under the 67th year of the reign of Emperor Nintoku (conventionally dated 379 AD), it is mentioned that in central Kibi Province, at a fork on Kawashima River (川嶋河, old name of Takahashi River in Okayama Prefecture), a great water serpent or dragon (大虬) dwelt and would breathe or spew out its venom, poisoning and killing many passersby.