Anciently, it was described with a monkey's mouth with small teeth like a fish’s, shining golden scales, and a quiet voice like a skylark or a flute.
Not much is known about the Ningyo.
Its flesh is pleasant-tasting, and anyone who eats it will attain remarkable longevity. However, catching a ningyo was believed to bring storms and misfortune, so fishermen who caught these creatures were said to throw them back into the sea. A ningyo washed onto the beach was an omen of war or calamity.