Final answer:
Japan has demanded the return of the Kuril Islands from Russia, but the matter remains unresolved despite offers for their repurchase.
Step-by-step explanation:
The country that has demanded the return of the Kuril Islands, a neighboring territory to Russia, is Japan. Following the end of World War II, the terms of Japan's surrender stipulated the relinquishment of various territories it had controlled, including the Kuril Islands, which were ceded to the Soviet Union (now Russia). Japan was heavily impacted by the war, with its infrastructure and economy devastated, leading to an agreement for Japan to have no military for offensive purposes. Despite offering a large sum of money, Japan's request for the return of the Kuril Islands remains unresolved, with the territory still under Russian control.