According to the annals of China and Ryukyu, the border between China and Ryukyu has been in cognitive awareness and practiced, and the Chiwei Island is the most eastern island of the group of the Diaoyutai Islands, Kume-jima is the westernmost island of the Ryukyu. Since 1885, the Japanese attempted to occupy the Diaoyutai Islands, took possession in 1895 and annexed to the domination of Okinawa. However, not only the Japanese had not completed the compilation of the domestic law for territories but also not according to the customary international law to circulate and publicize the information regarding the new occupation of the territory, thus revealing severe flaws. Through the historical data and analysis of the views of international law, this paper is to analyze the various legal arguments lodged by the Japanese government.