are a type of Japanese yōkai

Yōkai

are a class of supernatural monsters in Japanese folklore. The word yōkai is made up of the kanji for "otherworldly" and "weird". Yōkai range eclectically from the malevolent to the mischievous, or occasionally bring good fortune to those who encounter them...

 (folk legend ghosts) that appear in 18th century artist Toriyama Sekien

Toriyama Sekien

thumb|200px| was an 18th century scholar and ukiyo-e artist of Japanese folklore. He was the teacher of Utamaro and, before taking up printmaking, a painter of the Kanō school. Toriyama is most famous for his attempt to catalogue all species of yōkai in the Hyakki Yakō series.-References:...

's book Gazu Hyakki Yakō.

The aobōzu is depicted in the Gazu Hyakki Yakō as a one-eyed buddhist priest standing next to a thatched hut, however as there is no explanation of the image, the aobōzu's specific characteristics remain unknown.

It is believed that the aobōzu is the direct inspiration for the one-eyed priest hitotsume-kozō

Hitotsume-kozo

Hitotsume-kozō are monsters found in Japanese folklore. They are roughly the size of ten-year-old children, but otherwise resemble bald Buddhist priests...

 that is present in many yōkai drawings, such as Sawaki Suushi's Hyakkai-Zukan

Hyakkai-Zukan

is a collection of picture scrolls by Edo Period Japanese artist Sawaki Suushi. Completed in 1737, these scrolls are supernatural bestiaries, collections of ghosts, spirits and monsters, of which Suushi based on literature, folklore, other artwork. These works had a profound influence on subsequent...

published in 1737. There is also a theory that because the kanji ao (青) in its name also means inexperienced, it was depicted as a priest who has not studied enough.