Karafuto Prefecture
In 1906, after the Russo-Japanese War, following the Treaty of Portsmouth, the Southern Sakhalin was transferred to Japan. Ilyinskoye was renamed Kusunai and became part of Karafuto Prefecture. In 1945, following World War II, it was reoccupied by the Soviet Union. Administratively, on 2 February 1946 South Sakhalin Oblast was created, which was part of Khabarovsk Krai. Kusunai was renamed Ilyinsky, made an urban-type settlement, and included into Tomarinsky District. On 2 January 1947 South Sakhalin Oblast was abolished and merged into Sakhalin Oblast. On 1 January 2005, the urban-type settlement of Ilyinsky was downgraded to selo and renamed Ilyinskoye.