Kusshī, sometimes anglicized as Kussie, is a lake monster said to live in Lake Kussharo. Lake Kussharo is a 79 square kilometre, 387-foot deep caldera lake in eastern Hokkaido. Kusshī is described as reaching 30 to 60 feet in length, with dark brown, elephantine skin, a long neck, and a horse-like head. Witnesses who saw a Kusshī up close reported that they had silvery eyes and no visible ears.
Although mysterious creatures in Lake Kussharo have been mentioned as far back as Ainu folklore, the name was only coined in the 70s. In 1972, a man claimed to have witnessed what he initially thought was an overturned boat, until he saw it suddenly dive underneath the surface.
In July of 1974, A. Wada, a farmer, spotted a creature in Lake Kussharo. The creature was dark and had several humps about 13 feet apart. He watched the animal for some time until it dove underwater, leaving a large wake.
In September of 1974, a group of more than 15 people reported seeing a large animal swimming quickly below the surface of the lake. Unlike most other reports, this creature was described as being covered in shiny scales, rather than the more common dark, leathery skin.
Due to the increase of sightings throughout 1974, various TV crews and researchers started looking for any evidence of the creature. Several different groups reported seeing large moving objects more than 60 feet below the surface with fish finder sonar.
In July of 1975, a forestry worker who was on the shore of Lake Kussharo reported seeing an unusual creature. The animal, which he assumed was a horse, was quite far into the lake. As it got closer to him, he realized it was not a horse and was significantly larger. The creature then submerged, and he never saw it again.
In 1988, a man named Takashi Murata claimed to have been followed by a strange animal while in his motorboat on Lake Kussharo. The creature, which was only around 50 feet behind him, was described as very large, with dark skin and a back resembling a dolphin's. In 1997, a firefighter crew reported seeing a 60-foot long creature with a pike-like body and a dorsal fin 300 feet from shore in Lake Kussharo.
Lake Kussharo is a caldera lake, meaning it was formed from a volcano. Because of this, the heavy amount of sulphur in the lake has caused most of the aquatic wildlife to die out. The only surviving fish are eels, minnows, and the recently introduced rainbow trout. Theories as to the origin of Kusshī include misidentified swimming deer, vagrant seals or otters, and even surviving plesiosaurs or gigantic sea slugs.