Kassie is a cryptid reported from the Kagetsu River, Oita, Japan.
Description[]
In 2014, after heavy rains, an English cram school teacher spotted and photographed a large creature swimming in the Kagetsu River.
The water was muddy because of the rain, so all that could be seen was a dorsal fin-like section protruding from the surface of the water. The witness estimated the creature's size at 5 feet (1.5 meters) from its shadow. He felt that the creature was neither an eel nor a catfish.
According to the city museum, this could be a snakehead. Snakeheads are not native to Japan, but have been artificially introduced and are breeding over a wide area.