Uwan

In an old house, or a ruin, out of nowhere:

"UWAN!"

A shout with no shouter.

That's the creature. It is pure voice, and it is its own name — the yokai is called after the noise it makes, because the noise is all there is.

The Aomori account

A man named Kasuke and a companion are kept awake all night by a voice continuously echoing — shouting "uwan!"

And the detail that makes it:

The neighbours could not hear it.

A haunting calibrated to its victim.

Which is a much more disquieting proposition than a noise in an old house. The sound exists, and it is loud enough to keep two men awake all night, and it is addressed — it is happening to them and not to the house.

The defence, and its caveat

You'll read that you should shout it back — repeat what it says — and it flees.

The honest note: that comes from secondary sources with unclear provenance.

I'd still hold onto it, because it fits a grammar that runs right through the sound-yokai.

Answer the voice.

The mountain echo-spirit is dealt with by speaking to it, because it can only give back what it's given. The footsteps behind you on the road stop when you step aside and say "please, go on ahead" — and they pass, and continue up the road without you.

The rule for sounds in this tradition is not flee and not ignore. It's reply.

And then the painters needed something to draw

Here's why this small entry earns its place.

The 1737 scroll and Sekien's 1776 catalogue both show a blackened-toothed grotesque with both hands raised, mid-shout.

A body invented to carry a noise.

Because that's the problem a monster-cataloguer faces with a creature like this. The folklore is a sound. There is nothing to depict. And you are producing an illustrated book.

So somebody sat down and asked: what does a shout look like?

And the answer they arrived at — hands up, mouth open, leaning in — is the universal posture of saying boo.

Look at that plate knowing it, and it stops being a monster picture. It's a solution to a drawing problem, and a rather good one.

It belongs to a family

The sound-yokai are, collectively, the smallest creatures in the tradition and the ones that explain all the others.

Beans being washed by a river at night, endlessly. Footsteps with nobody walking. Sand falling out of shrine trees with no thrower. Something brushing your shins in the rain. A tree being felled in a forest where, by morning, nothing has been cut.

And a shout.

Each is one sensory occurrence plus a name. No body, no motive, no story.

Which is the smallest a yokai can be — and, if you follow it far enough, what all of them are underneath.