Aobōzu (青坊主, Blue Priest) are a type of Japanese yōkai (folk legend ghosts) that appear in 18th century artist Toriyama Sekien's book "Gazu Hyakki Yakō."
In the 4th anime, he was exactly just like the original panting.
In the 5th anime, he has a body, blue hair, and doesn't stick out his tongue.
Aobōzu appeared in episode 17 of the 5th anime adaption along with Kokon.
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-kozōthat is present in many yōkai drawings, such as Sawaki Suushi's "Hyakkai-Zukan" 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.
- He was called Aoi for the first few times he appeared.