Analysis of information sources in references of the Wikipedia article "Soviet–Japanese Joint Declaration of 1956" in English language version.
Within Japan it is sometimes suggested that this agreement could serve as the starting point of a process that could ultimately lead to the return of more than just two islands. This was, for instance, the proposal of Foreign Minister Watanabe during the early 1990s (Hasegawa 1998: 461). This is, however, entirely to misinterpret how the statement was intended and how it continues to be understood by proponents within Russia. For the Russian side, the 1956 Joint Declaration is significant not in serving as some initial step towards resolution, but rather in providing a decisive end to the dispute. The intended meaning is very clearly that the two smaller islands would only be transferred (note the use of "transfer" rather than "return") at some point after the conclusion of a peace treaty in which the borders of the two countries would be definitively demarcated. In effect then, Japan is being asked to give up its claims to the disputed territory and, in exchange, as a gesture of goodwill and not as a response to legal obligation, Russia would transfer Shikotan and Habomai. What is more, this would be the full extent of the Russian concessions. The Russian side will no longer countenance any further sweeteners (any "plus alpha") with regard to the other two islands, such as a promise of demilitarisation or any special arrangements that hint at recognition of the legitimacy of Japan's claims.
In 1956, on the occasion of the restoration of bilateral diplomatic relations, Moscow officially stated that it was willing to transfer the two smaller islands to Japan following the conclusion of a peace treaty. As confirmed by Vladimir Putin in 2000 and again in 2012, this remains Moscow's position (Soejima and Komaki 2012). Japanese leaders, however, have consistently refused to accept this offer, drawing attention to the fact that Shikotan and Habomai represent only 7 percent of the disputed territory (Prime Minister Noda cited in Nihon Keizai Shinbun 2012). Despite the passage of much time and considerable diplomatic effort, the sides have essentially been unable to proceed beyond this impasse.
1956 Joint Declaration, which was ratified in the Soviet Union, was also ratified in Japan. So, when today you say "we don't want two islands, we want four", this looks somehow strange to me. Why did you ratify [the Declaration] then?
Khrushchev: The Soviet side is generally in agreement with proposed draft. We want to meet the wishes of Japan, so we are ready to drop the clause regarding transfer of Okinawa and other [US-administered] territories to Japan from our draft. We only have one reservation, merely of wording: we ask [Japan] to drop expression "including territorial question" from the first section of Japanese draft. We propose so, because otherwise it may be thought, that there exists some other territorial question between Japan and the Soviet Union besides Habomai and Shikotan. This might lead to rumors and misinterpretation of documents which we are about to sign.