Kawauso.

Kawauso (獺, かわうそ) begins as an otter but becomes something much more flexible in folklore. Old otters gain transformative power, and their sleek river bodies become the base for a range of deceptions. They may appear as children in oversized hats, beautiful women near the water, strange monks, severed heads, or barely convincing human figures whose speech quickly gives them away.

Even when disguised, they retain a playful instability. A kawauso never feels as polished as a kitsune. The yōkai's charm lies in almost getting the human form right, then collapsing into nonsense, mimicry, or laughter. That imprecision keeps the creature close to the banks and roads where surprise matters more than elegance.

Most kawauso stories are built from pranks. The yōkai calls a person's name from the dark, repeats words back in a mocking voice, snuffs out lanterns, or lures strangers into absurd confrontations with stumps, rocks, and shadows. It is fond of confusion for its own sake, and much of its folklore lives in that low register of night-time embarrassment rather than outright terror.

A darker current runs beneath the playfulness. In some Ishikawa stories, a kawauso becomes a beautiful woman to lure men to the moat or water's edge and devour them. Elsewhere it possesses humans, drains their strength, or blurs into kappa-like water danger. This makes the otter yōkai slippery in moral tone, often comic, sometimes predatory, and always difficult to classify cleanly.