The Ainu are Japans' largest ethnic minority.
They are known for
Shamanistic beliefs and practises which
are considered part of the Siberian tradition.
Shamanism is probably one of the sources of Shinto,
the indigenous religion of the ethnic Japanese.
Specimens of Ainu Folk-lore
by Basil Hall Chamberlain 
This is a collection of Ainu folktales, by the translator of the Kojiki.
by John Batchelor [1888-1893]
Another collection of Ainu folktales, by a Christian missionary who
lived among them for many years; these translations are considered
primary source material to this day.
Yukara, epos of the Ainus
by Kiyoko Miura.
Kutune Shirka, The Ainu Epic
tr. by Arthur Waley 
NOTE: The preceeding two texts have unknown copyright status.