1. Hokkaido Island

2. Shikoku Island

Correct answer: Hokkaido Island.

Hokkaido is the northernmost of Japan's four main islands.

The so-called "four northern islands" is Japan's statement, and Russia calls it the South Kuril Islands, which refers to the four islands in the south of the Kuril Islands, namely, Choishou, Sedan, Tooth Dance and Guohou.

In the late World War II, in order to repay the Soviet Union for sending troops to attack Japan, the Soviet Union, the United States and Britain stipulated in the Yalta Agreement: "The Thousand Islands must be handed over to the Soviet Union." Since then, the Soviet Union (including now Russia) has been actually controlling the above-mentioned territories. However, Japan believes that it has never given up the request to recover the "four northern islands".