It is believed that the root of Japanese religion, AND the root of Japanese performing arts lie in shamanic trance. Shamanic kagura was once commonplace throughout Japan, but was suppressed by the Meiji government. Only one place in Japan still has traditional shamanic kagura and that happens to be the place I live. I will be posting a lot more on this subject as it is the focus of a lot of my research and there is almost nothing on it in English.
The focus of Omoto kagura is Omoto, or Omotojin, the local land-based kami. Up in Izumo it is called Kojin, and like Omoto is represented as a rope snake. There are about 60 sites in my area that are considered Omoto shrines, though only a few have shrine buildings. Omoto kagura is practised at a handful of shrines, each shrine working to a 5, 6, or 7 year cycle, so some years there is no Omoto kagura , some years several performances.
Omoto kagura is performed by priests, and in fact all the priests of the county take part. As in the old days, the villagers perform theatrical kagura during the intervals between the priests various dances.
The supreme importance of Omoto kagura to the area is indicated by the number of offerings on the altar. I counted more than 40 different things on the altar at this performance in Ichiyama, compared with less than a dozen at a normal ceremony.
The dance in the video is called Tsunanuki (rope-pulling) and is probably the most well known of the various dances. If an Omoto kagura is successful then someone will be possessed by Omotojin and will answer questions by the priests usually on such matters as the coming years agricultural cycle, upcoming dangers etc. The grandfather of a friend of mine became possessed by Omotojin on 5 different occasions in the last half of the 20th Century.