Nobusuma (野衾)

Edo-period encyclopedic and illustrated sources treat the nobusuma as a kind of yōkai linked to nocturnal mammals: some entries and images identify it with musasabi (flying squirrels) while other textual traditions describe a life-cycle in which bats age into nobusuma and later into a yamachichi. Sources present these identifications and transmutation ideas side by side rather than as a single canonical origin.

Descriptions vary across sources and illustrations. Toriyama Sekien's Konjaku Gazu Zoku Hyakki depicts a flying-squirrel–like creature with fleshy wings that, when folded, resemble bat wings; other texts and illustrations render it more batlike or rat-colored and small in form. Woodblock depictions sometimes show a small winged beast that can come to lie upon or cover a person's face with its forepaws.

Sources report a range of behaviors: some accounts say it will latch onto a human and cover the eyes and mouth, in some variants to feed on blood; other traditions (via a later form, yamachichi) say an aging bat will suck the breath from a sleeping person, potentially causing death if unwitnessed. Illustrated and textual sources also record a behavior of biting off or extinguishing the tip of a torch carried by a traveler and seemingly 'breathing' or consuming the flame. Other reports identify attacks on animals (for example cats) in local legends.