The Ainu are an ethnic group comprising related Indigenous peoples who are native to northern Japan, including Hokkaido and Northeast Honshu, as well as the land surrounding the Sea of Okhotsk, such as Sakhalin, the Kuril Islands, the Kamchatka Peninsula, and the Khabarovsk Krai; they have occupied these areas known to them as "Ainu Mosir", since before the arrival of the modern Japanese and Russians. These regions are often referred to as Ezochi (蝦夷地) and its inhabitants as Emishi (蝦夷) in historical Japanese texts.

The Kuril Islands or Kurile Islands are a volcanic archipelago administered as part of Sakhalin Oblast in the Russian Far East. The islands stretch approximately 1,300 km (810 mi) northeast from Hokkaido in Japan to Kamchatka Peninsula in Russia, separating the Sea of Okhotsk from the north Pacific Ocean. There are 56 islands and many minor islets. The Kuril Islands consist of the Greater Kuril Chain and, at the southwest end, the parallel Lesser Kuril Chain. They cover an area of around 10,503.2 square kilometres (4,055.3 sq mi), with a population of roughly 20,000.