The Un (口云) are Mushi that eat sound.
They usually live in deep forests, but when the winter comes and the snow dampens the sound, they begin living near humans. They infest the inner ear canal and eat sound, and resemble snail shells (which wind clockwise) in their dormant form. They are partners of the Ah.
When they attach themselves to a host, they consume the sound that would normally enter the ear, causing deafness in the infested ear.
These Mushi are driven out with brine (salt dissolved in hot water).