noun
blue demon; blue ogre
A demon or ogre with blue skin, often depicted with horns. In folklore and modern media, blue oni are frequently paired with red oni (赤鬼).
節分には、赤鬼と青鬼の面をかぶることもある。
During Setsubun, people sometimes wear red and blue demon masks.
昔話に、心優しい青鬼が登場する。
A kind-hearted blue ogre appears in the old tale.
Compound of 青 (あお, 'blue') and 鬼 (おに, 'demon, ogre'). The exact origin of the blue oni in folklore is uncertain, but the pairing of red and blue oni is a common motif.