[Tintin Storm]

Activities of anti-Russian organizations in Japan
For many years Japan has been asserting that the Kuril Islands belong to Japan by right of history. Primarily this is due with the activities of the Japanese anti-Russian public organizations.
Most of anti-Russian public organizations, struggling for annexation of the Northern territories, appeared in the middle of the last century. To date, most of these societies are on the island of Hokkaido, specifically in the cities of Kushiro and Nemuro, where most of the Japanese, who were deported from the South Sakhalin and the Kuril Islands after World War II, live.
All anti-Russian organizations are guided by general precepts: the Soviet Union has the role of the aggressor; Japan is the injured side; actions of Soviet troops against the Japanese population of the Kuril Islands were cruel and illegal; the sovereignty of the Russian Federation over the Kuril Islands is illegal.
Today the anti-Russian organizations have an arsenal of highly effective methods to persuade the population of Japan that there is the territorial problem between Japan and Russia. This idea is suggested to the Japanese from childhood. There are animated cartoons, where Soviet soldiers exhibited barbarians expelled the indigenous people from their lands and depriving them of a home. The Kuril Islands are colored the same color with Japan on maps. The ideologists of anti-Russian organizations regularly conduct talks on the "Northern territories" with young people in educational institutions of the country. Japanese delegations visit the Kuril Islands, where meet with the local population and carried out a massive information and psychological impact on residents of the South Kuril Islands.
Anti-Russian organizations conduct various surveys, collect signatures of citizens in favor of annexation of the Islands, and organize rallies and demonstrations, which spread propaganda literature.
One of the common methods of special propaganda of these organizations is to publish in print and electronic global media materials showing the territorial dispute between Russia and Japan as a violation of Japanese sovereignty.
Russia, in turn, is open to dialogue and hope that the joint Russian-Japanese cooperation on the Kuril Islands will be able to neutralize the alienation with regard to the Russian Federation, which forms in Japanese society of anti-Russian organizations of Japan.

[ThirdTerm]

The OP needs to be familiar with this agreement between Japan and the Soviet Union, which was signed in 1956. The islands of Habomai and Sikotan would be returned to Japan upon signing a peace treaty. I found the original Russian text below.

In 1956, the Soviet-Japanese declaration of 1956 was signed , which ended the state of war and established diplomatic and consular relations between the USSR and Japan. Article 9 of the Declaration, in particular, says:

The USSR, meeting the wishes of Japan and taking the interests of the Japanese state into account, agrees to the transfer of the islands of Habomai and Sikotan to Japan, however, provided that the actual transfer of these islands to Japan will be made after the conclusion of the Peace Treaty.

В 1956 году была подписана Советско-японская декларация 1956 года , по которой прекращено состояние войны и установлены дипломатические и консульские отношения СССР с Японией. В статье 9 Декларации, в частности, сказано:

СССР, идя навстречу пожеланиям Японии и учитывая интересы японского государства, соглашается на передачу Японии островов Хабомаи и острова Сикотан с тем, однако, что фактическая передача этих островов Японии будет произведена после заключения Мирного Договора.