AMEMASU

Lore

Amemasu is a yokai said to inhabit Japan's rivers and lakes. At first glance, it appears to be nothing more than an ordinary trout—until it reveals its sinister ability to grow to colossal size. Some tales insist that Amemasu is actually a guardian spirit of a particular body of water, choosing the form of a fish for unknown reasons. Others proclaim it the "king of trout," a monstrous ruler of all salmon and river fish.

Legends speak of Amemasu traveling upstream to attend a water festival held every year on November 15. On the night before the festival, locals stop using their baths and halt any waterwheels. Fishermen pull up their nets—or, if there is no time, they slash them apart—so as not to hinder the great fish's passage. Those who dare to eat a salmon accidentally caught during this time face a terrible generational curse. On the autumn equinox of that year, people say you can hear eerie cries from the riverbanks: "We are going upstream!" Anyone who hears this voice is doomed to certain death. In some regions, fear of this story is so strong that people refuse to eat salmon at all.

When Amemasu settles in a lake and continues to grow, it can become a vengeful yokai that harbors a deep grudge against fishers who intrude with nets and rods. Tales abound of lone anglers on small boats heading toward a favored fishing spot, only to vanish in a sudden whirlpool. Later, splintered fragments of their boat float to the surface—a grim sign that some vast, ten‑meter beast lurks beneath, sated on its recent catch. Villagers warn that it could swallow a horse whole if the animal strayed too close to the water's edge.

If such a fish outgrows a modest lake, it may no longer swim freely at all, its head resting on one bank while its tail brushes the opposite shore. On larger lakes, its enormous dorsal fin is said to slice through the surface like a drifting black ridge. Woe to anyone nearby if Amemasu stirs—its movement can churn the depths, raise devastating waves, and even shake the surrounding land like an earthquake.