Traditional Ainu religion sees the world as shared between humans (ainu) and kamuy, spirit-beings who visit the human world wearing the forms of animals, plants, tools and natural forces. A bear, a fire, a boat or a storm is the temporary body of a kamuy, and right conduct toward it decides whether the visitor returns to the land of the spirits speaking well or badly of its human hosts. The hearth goddess Kamuy-huci, keeper of the household fire, stands closest to people and carries prayers upward to the other kamuy; Kim-un Kamuy, the bear god of the mountains, and Repun Kamuy, the orca god of the open sea, preside over the animals on which Ainu hunting and fishing depended.
Worship centered on the household rather than on a temple or a professional priesthood. Offerings of whittled willow wands called inaw, with libations of sake, accompanied prayers spoken by the male head of a house, while women tended the hearth on which everything turned. The most famous ceremony, the iyomante or bear-sending, raised a bear cub within the community and then ritually sent its spirit home laden with gifts, an act of hospitality between species that Neil Gordon Munro documented in detail among Hokkaido communities before the Second World War.
The Ainu carried their theology in oral literature rather than scripture: yukar, long chanted epics in which kamuy and heroes speak in the first person, preserved cosmology, ritual instruction and history together. Donald Philippi's translations brought these songs of gods and humans to English readers, and epic chanting, nearly silenced during the assimilation era, is now part of a deliberate Ainu cultural revival.