Nuppeppō look like blobs of flesh. Their exact form varies, although the folds of their skin often look like body parts such as fingers, toes, or even a face. These creatures are thought to roam deserted areas such as temples and graveyards. They are mostly active at night and tend to be solitary.

Despite its disturbing appearance, the nuppeppō is mostly harmless and is in fact a peaceful creature. However, its pungent odor has been known to frighten people and possibly cause them to faint from the sheer potency of its stench. This is hardly surprising since nuppeppō smell like rotting flesh. In fact, nuppeppō smell so bad that some people believe that they are actually made of corpses.

FUN FACT: It is said that those who eat the flesh of nuppeppō will be granted eternal youth. Obtaining this flesh is quite difficult since nuppeppō are notoriously hard to catch. Keeping the flesh down once it has been consumed is even more difficult because it smells and tastes disgusting.

Examples in various media:

Uboa (Yume Nikki) This is a rare example of a malicious nuppeppō. He traps the protagonist of Yume Nikki in an inescapable world. This character inspired many other characters in various works including Undertale's W. D. Gaster.

Unnamed Nuppeppō (Yokai Monsters: Spook Warfare) This movie is quite old, so I had trouble finding a picture of the nuppeppō. You can see the nuppeppō slightly to the left of the bottom center of this movie poster. It's the creature that looks like a lump of clay.