As a historian specializing in East Asian studies, I have a deep understanding of the political and social dynamics that shaped Japan during the early 20th century. When discussing the leadership of Japan during World War I, it is important to clarify that Japan was not directly involved in the war until later years, and its leadership structure was quite different from the major powers that were engaged in the conflict from the onset.

Step 1: English Answer
The leader of Japan during World War I was not a singular figure but a series of political leaders who held the position of Prime Minister (首相, Shushō) during the period. The Prime Minister in Japan is the head of government under the constitutional monarchy, and the role involves leading the Cabinet and overseeing the administration of the country.

Okuma Shigenobu, as you mentioned, was indeed a prominent figure in Japanese politics around the time of World War I. He served as the Prime Minister for a brief period in 1914, but his tenure was not directly tied to the war. Okuma is perhaps better known for his role in the formulation of the "Twenty-One Demands" towards China, which were a set of proposals that Japan presented to the government of China in 1915, aiming to expand Japanese influence in China. These demands were a significant point of contention and are often considered a part of Japan's broader imperial ambitions in East Asia.

However, Okuma was not the leader of Japan for the entirety of World War I. The country had several Prime Ministers during the war years, including Terauchi Masatake, who served from 1916 to 1922 and played a significant role in Japan's participation in the war. Japan joined the war on the side of the Allies in 1914, primarily against Germany, and Terauchi's administration was responsible for the decision to participate in the conflict.

Matthew C. Perry, on the other hand, was a figure from a much earlier era. Perry was a U.S. naval officer who is most famous for his role in the opening of Japan to the West. He led a diplomatic mission to Japan in the 1850s, resulting in the signing of the Convention of Kanagawa, which ended Japan's isolationist policy and opened the country to trade with the United States. While Perry's impact on Japan was profound, his role was not directly related to World War I, which occurred nearly seven decades after his mission.

In summary, the leadership of Japan during World War I was a complex affair with multiple Prime Ministers serving during the war years. Okuma Shigenobu was one of them, but his role was not primarily defined by the war. Instead, it was figures like Terauchi Masatake who were more directly involved in the war effort.

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--kuma Shigenobu- was Prime Minister at the beginning of World War 1 . He is also responsible for the Twenty- One Demands with China. Matthew C. Perry- Played a leading role in the opening of Japan to the West with the Convention of Kanagawa.Apr 9, 2013read more >>