Akugyo

Akugyo are presented within Japanese yōkai taxonomy as supernatural sea‑beings rather than ordinary animals. There is no single cosmogonic origin recorded in the supplied sources; instead, akugyo appear in localized maritime legends as hostile, person-like marine threats whose name (悪魚, "evil fish") marks them as malign piscine entities. Variants of the concept align them with enlarged ningyo or with thunder‑associated monstrous fish (raichōgyo), reflecting hybrid imagery common to yōkai.

Accounts vary. Akugyo are consistently described as enormous in size (one reported specimen measured roughly 11 meters in body length with horns over 60 centimeters). Some are described simply as gigantic fish; other variants resemble oversized ningyo with gold and silver scales. The mermaid‑type akugyo variants are often said to bear a pair of white, oni‑like horns on the head. Some individual accounts also describe akugyo that breathe fire.

Akugyo are known in the lore to capsize entire ships and to eat drowning sailors. Fishermen report that boats can become lodged between an akugyo's fins, leaving crews vulnerable to being taken. Some akugyo are described as breathing fire. Stories emphasize their enormous strength and endurance—the cited Echigo episode reports that a large military force was required to slay one specimen in that narrative. In a named anecdote, a taiko drummer (Izutsuya Kanroku) beat his drum loudly and his boat was shaken loose from an akugyo, allowing escape.