Matsumae clan
In the Edo period, Hokkaidō was assigned to the provincial government of the Matsumae clan. Ainu were forced into laboring for one-seventh to one-fifth pay by Matsumae retainers, which the Ainu regarded as slavery. Nibutani Ainu were taken as slaves to Atsukeshi, over 350 kilometers away on the other side of the island. Work-related deaths had reduced the eastern population of Ainu, leading to labor relocation from the Saru and Yufutsu areas.