The Nuppeppo is passive and unaggressive. The body odor is said to rival that smell of rotting flesh. Other theories claim that the Nuppeppo is actually decaying flesh. There is a rumor that states that those who eat the flesh of a Nuppeppo shall have eternal youth. Some sources, however, claim that eating it instead grants eternal life, though sometimes say that the form of eternal life is the Nuppeppo, and anyone who eats it, becomes it.
The Nuppeppo aimlessly wanders deserted streets of villages, towns and cities, often at night towards the year-end, or graveyards or abandoned temples. It is normally solitary, but there are sightings of them in groups.
Fingers and toes may be attributed as features amidst of fold of the skin.