Nurikabe are yōkai that resemble invisible walls. When depicted in art, it is often portrayed as a white or gray wall with facial features. This yōkai is thought to be an explanation for why travelers lose their bearings on long journeys. 

This yōkai is known to impede travelers at night. It will block a person's path and refuse to move. It is impossible to climb over or around this yōkai as it will simply stretch its body to continue blocking the person's path. However, some say that hitting the bottom left part of this yōkai with a stick will make it disappear. Hitting it anywhere else won't have any effect on it.

FUN FACT: Sometimes, tanuki will shapeshift to resemble this yōkai. However, while nurikabe have no impact on what someone can see since they are invisible, tanuki will prevent people from seeing in front of themselves in addition to blocking their path.

Examples in various media:

Nurikabe (Gegege no Kitarō)

Noway (Yo-kai Watch)

Whomp (various Mario games)