Eddie is a cryptid that is believed to inhabit the Edo River, which runs through Ibaraki, Saitama, Chiba, and Tokyo prefectures in Japan.
Description[]

Newspaper blurb about Eddie as a nickname for the black carp
In the late 1990s, a local fishing club gave the nickname Eddie to one of the largest black carp in the Edo River. Black carp are not native to Japan, but some of them were brought from China and released into the Edo River, where they have been breeding.
Originally, the name Eddie was only a nickname for the black carp, but it was later appropriated for the cryptid when a huge fish of extraordinary size was spotted in the Edo River.
In 2000, a fish over 2 meters long was seen swimming in the Edo River with its caudal fins protruding from the surface of the river on several occasions.

2010 report
On December 9, 2010, the Japanese forum "2ch" reported the sighting of a 10 meter fish swimming under the Katsushika Bashi Bridge over the Edo River. The reliability of this information is unknown because it is an anonymous report uploaded to a place where anyone can post, and the size of the Eddie is much larger than in other sightings.