Nyoijizai is a Japanese specter included in a specter art collection book entitled "Hyakki Tsurezure Bukuro" by Sekien TORIYAMA and is a kind of the Tsukumo-gami (a specter changed from a utensil).
Nyoi-butsugu' is a Buddhist altar article which looks like a magonote (backscratcher) and Nyoijizai specter was created by changing the Nyoi. Nyoijizai has a Nyoi on its head, the shape of its body is close to that of the human, and its fingers are equiped with sharp nails. It is said to be a specter which scratches with a long arm and fingers the itchy spots just like the backscratcher does, but it also is said that, if one is not careful, one may be painfully hurt.
It is said that, since "Hyakki Yagyo Emaki" of the Muromachi period contains the drawing of a Nyoi flying in the sky, Sekien drew this specter based on the book just like many of Tsukumo-gami included in the "Hyakki Tsurezure Bukuro."