Nurikabe

The nurikabe (ぬりかべ) is a Yōkai, or spirit, from Japanese folklore. It manifests as a wall that impedes or misdirects walking travelers at night. Trying to go around is futile as it extends itself forever. Knocking on the lower part of the wall makes it disappear.^[1] It has been suggested that the legend was created to explain travellers losing their bearings on long journeys.^[2]