Ainu, EYE noo, are a group of people who may have been the first inhabitants of what is now Japan. There are about 15,000 Ainu. Most of the Ainu live on Hokkaido, Japan's northernmost main island. In the mid-1900's, many Ainu moved to Hokkaido from Sakhalin and the Kuril Islands. Sakhalin is a part of Russia. Russia claims and occupies all the Kurils, but Japan claims the southernmost ones.