AC— Atlas of Cryptids
Case file Nº044 // Open since 1978Class 3

Issie

Aliases: Isshii · Lake Ikeda monster / Territory: Japon

Dark humps seen on Japan's Lake Ikeda since 1978; ambiguous photos, very real giant eels, and no confirmation.

Lake Ikeda is a deep caldera lake at the southern tip of Kyūshū, close to the hot-spring resort of Ibusuki in Kagoshima Prefecture. It is the island's largest lake, and its volcanic isolation — no significant river flows in or out — has always lent it an air of the sealed and unknowable. The monster attributed to it since 1978 carries a nickname built squarely on the Nessie template: Issie, in Japanese Isshii.

A folk story told around the lake concerns a white mare whose foal was stolen by a samurai: grief-stricken, she threw herself into the water and became a giant creature that still surfaces to look for her young. The tale belongs to Kyūshū's regional folklore and predates the media monster, for which it later provided a convenient pedigree.

The modern case opens on September 3, 1978, when some twenty people gathered on the shore — several of them relatives — reported watching two black humps travel fast across the surface. National media picked it up. That December, Toshiaki Matsuhara photographed a dark shape amid swirling water; further photos and a video followed in 1991. All of this imagery, shot from a distance at low resolution, has defied identification, with readings ranging from animal to waves to floating debris.

The strongest explanation already swims in the lake. Ikeda is known for its large eels — giant mottled eels approaching two metres, live specimens of which are displayed nearby. The back of a massive eel, a wave train whipped up by caldera winds, or a drifting log can account for every reported sighting. The town of Ibusuki, which has raised an Issie statue on the shore and adopted the creature as a tourism emblem, makes little secret of the promotional dimension. No serious report has followed the early 1990s.

+ Notable reports

  1. // Lake Ikeda shoreline, Kagoshima

    About twenty witnesses gathered at the lake describe two dark humps speeding across the surface. Nationwide coverage launches the name Issie.

  2. // Lake Ikeda

    Toshiaki Matsuhara photographs a black shape surrounded by disturbed water. Taken from afar, the image remains indeterminate — animal, wave or debris.

  3. // Lake Ikeda

    A video sequence shows a dark object moving at the surface. Like the 1978 photographs, it has yielded no identification and splits opinion between wake effects and a known animal.

+ Leading rational explanations

  • The lake's well-documented giant mottled eels, approaching two metres, whose backs sometimes break the surface
  • Wave trains and swirls raised by wind inside an enclosed caldera
  • Drifting logs and floating debris
  • Open tourism promotion by Ibusuki: statue, merchandise, careful tending of the legend
  • The white-mare folk tale retrofitted as an ancient 'monster tradition'

Status note

Class 3 — Disputed physical traces

Class 3: genuine but unreadable photographs and video count as contested physical traces; everything else is testimony, and a candidate explanation — the giant eels — already lives in the lake.

+ Frequently asked questions

Is Issie real?
No evidence establishes it: the 1978 photos and 1991 video are too distant to identify, and nothing else has surfaced. The lake does, however, hold genuinely huge eels, which remain the most economical explanation for the humps people report.
What happened on September 3, 1978?
About twenty people on the shore of Lake Ikeda said they watched two black humps move quickly across the surface. That collective sighting launched the case and the nickname Issie, coined after Nessie.
What does a white mare have to do with Issie?
A local tale says a mare whose foal was stolen leapt into the lake and became a giant creature. That Kyūshū folk story predates the 1978 media monster, which borrowed it afterwards as a backstory.

Sources