Rise of the Nakamura
A supernatural beast that usually takes the form of a huge, muscular, bestial human. Oni come in many varieties, some similar to naturally occurring species, while others are little more than spirits. They inhabit wooded and mountainous areas, usually making a den in a cave or abandoned structure, where they attack travelers, eat them, and collect their skulls.
While passing through the mountains in the Northern part of Shimosa Province, the Nakamura army was attacked by a feral Oni. It was defeated and killed by Gouta and the Nakamura Demon Squad, after which the half-giant took its kanabou as a trophy.
Ajibana Chinatsu, one of the ninja working under Yamada Junko is known to be able to use magic to summon an Oni. This type is a spiritual beast, and, when summoned, blindly wreaks havoc until it is dismissed or banished.