The name means the kamuy of the mountains, and the mountains in question are the wooded interior of Hokkaido, above and behind the river settlements where the Ainu lived. He is the most consequential visitor in the system, and he arrives as a bear.
The distinction the tradition draws, and that outside accounts have flattened for a century and a half, is between the visitor and the costume. A bear encountered in the forest is a kamuy in a bear's body, and the body is a gift being delivered. Meat and fur are not taken from an animal; they are received from a guest who brought them, having gone to the trouble of putting them on. What that produces is not a hunting religion in the ordinary sense but a set of obligations of hospitality, in which the correct handling of the remains matters as much as the hunt.
The kamuy yukar make this explicit, because in them the bear speaks. He describes coming down, describes what the household did, and states whether he will return. A poor reception is reported back in the land of the kamuy and has consequences for the household, which puts a great deal of weight on conduct that a European reader would file as table manners.
The brown bear of Hokkaido is a genuinely dangerous animal, and none of this is sentimental. It is a way of holding together the facts that the bear is powerful, that killing it is necessary and that killing it incurs a debt.