Japan accelerated its invasion and external expansion after the Meiji Restoration. Japan seized Ryukyu in 1879 and changed its name to Okinawa Prefecture. Soon after that, Japan began to act covertly to invade and occupy Diaoyu Dao and secretly "included" Diaoyu Dao in its territory at the end of the Sino-Japanese War of 1894-1895. Japan then forced China to sign the unequal Treaty of Shimonoseki and cede to Japan the island of Formosa (Taiwan)， together with Diaoyu Dao and all other islands appertaining or belonging to the said island of Formosa.

In 1884, a Japanese man claimed that he first landed on Diaoyu Dao and found the island to be uninhabited. The Japanese government then dispatched secret facts-finding missions to Diaoyu Dao and attempted to invade and occupy the island. The above-mentioned plots by Japan triggered China's alert. On September 6, 1885 (the 28th day of the 7th month in the 11th year of the reign of Emperor Guangxu of the Qing Dynasty)， the Chinese newspaper Shen-pao (Shanghai News) reported: "Recently, Japanese flags have been seen on the islands northeast to Taiwan, revealing Japan's intention to occupy these islands." But the Japanese government did not dare to take any further action for fear of reaction from China.

After the secret facts-finding missions to Diaoyu Dao, the governor of Okinawa Prefecture sent a report in secrecy to the Minister of Internal Affairs Yamagata Aritomo on September 22, 1885, saying that these uninhabited islands were, in fact, the same Diaoyu Tai, Huangwei Yu and Chiwe Yu that were recorded in the Records of Messages from Chong-shan (Zhong Shan Chuan Xin Lu) and known well to imperial title-conferring envoys of the Qing court on their voyages to Ryukyu, and that he had doubts as to whether or not sovereignty markers should be set up and therefore asked for instruction. The Minister of Internal Affairs Yamagata Aritomo solicited opinion from the Foreign Minister Inoue Kaoru on October 9. Inoue Kaoru replied in a letter to Yamagata Aritomo on October 21, "At present, any open moves such as placing sovereignty markers are bound to alert the Qing imperial court. Therefore, it is advisable not to go beyond field surveys and detailed reports on the shapes of the bays, land and other resources for future development. In the meantime, we will wait for a better time to engage in such activities as putting up sovereignty markers and embarking on development on the islands." Inoue Kaoru also made a special emphasis that "it is inappropriate to publicize the missions on official gazette or newspapers." As a result, the Japanese government did not approve of the request of Okinawa Prefecture to set up sovereignty markers.

The governor of Okinawa Prefecture submitted the matter for approval to the Minister of Internal Affairs once again on January 13, 1890, saying that Diaoyu Dao and other "above-mentioned uninhabited islands have remained under no specific jurisdiction", and that he "intends to place them under the jurisdiction of the Office of Yaeyama Islands." On November 2, 1893, the governor of Okinawa Prefecture applied once again for setting up sovereignty markers to incorporate the islands into Japan's territory. The Japanese government did not respond. On May 12, 1894, two months before the Sino-Japanese War, the secret facts-finding missions to Diaoyu Dao by Okinawa Prefecture came to a final conclusion, "Ever since the prefecture police surveyed the island in 1885 (the 18th year of the Meiji period)， there have been no subsequent investigations. As a result, it is difficult to provide any specific reports on it... In addition, there exist no old records related to the said island or folklore and legends demonstrating that the island belongs to our country."

Japan's attempts to occupy Diaoyu Dao were clearly recorded in Japan Diplomatic Documents compiled by the Japanese Foreign Ministry. Relevant documents evidently show that the Japanese government intended to occupy Diaoyu Dao, but refrained from acting impetuously as it was fully aware of China's sovereignty over these islands.

Japan waged the Sino-Japanese War in July 1894. Towards the end of November 1894, Japanese forces seized the Chinese port of Lushun (then known as Port Arthur)， virtually securing defeat of the Qing court. Against such backdrop, the Japanese Minister of Internal Affairs Yasushi Nomura wrote to Foreign Minister Mutsu Munemitsu on December 27 that the "circumstances have now changed", and called for a decision by the cabinet on the issue of setting up sovereignty markers in Diaoyu Dao and incorporating the island into Japan's territory. Mutsu Munemitsu expressed his support for the proposal in his reply to Yasushi Nomura on January 11, 1895. The Japanese cabinet secretly passed a resolution on January 14 to "place" Diaoyu Dao under the jurisdiction of Okinawa Prefecture.

Japan's official documents show that from the time of the facts-finding missions to Diaoyu Dao in 1885 to the occupation of the islands in 1895, Japan had consistently acted in secrecy without making its moves public. This further proves that Japan's claim of sovereignty over Diaoyu Dao does not have legal effect under international law.

On April 17, 1895, the Qing court was defeated in the Sino-Japanese War and forced to sign the unequal Treaty of Shimonoseki and cede to Japan "the island of Formosa (Taiwan)， together with all islands appertaining or belonging to the said island of Formosa". The Diaoyu Dao Islands were ceded to Japan as "islands appertaining or belonging to the said island of Formosa". In 1900, Japan changed the name of Diaoyu Dao to "Senkaku Islands".