Adachi Asumu is a boy who is almost done with middle school. During a trip to his relatives, he meets a rather odd man just loosely named Hibiki. When Asumu's cousin is kidnapped by the Makamou, ancient monsters who threaten people, the oddball Hibiki saves the day in his true form, an Oni, field agents of the Makamou extermination group Takeshi. From that day on, Asumu follows Hibiki's steps as well as his co-workers at Takeshi, the young yet wise Ibuki and the courageous rookie Todoroki. 2005 is definitely quite a year for Adachi Asumu in this action-packed drama.