At least in the Pacific Japan seized upon World War I as a means for taking control of the German colonies in Micronesia (or today, the nations of Palau, Marshall Islands, Northern Marianas (US), and Federated States of Micronesia). Generally speaking there were no great battles in the Pacific during the first world war; a couple German cruisers bombarded the French colonial capital of Papeete (French Polynesia) and sank a couple of French vessels.

One of the most interesting WWI wrecks you can go scuba diving on is the SMS Cormoran. The ship was a German merchant raider during the First World War- though virtually as soon as the war began the Japanese navy began hunting it off the coast of China. The Cormoran made it out to the open ocean and tried to resupply at the American naval colony of Guam where they were refused, but reportedly treated well as they could not leave Apra harbor without running into the Japanese- who had seized all of the other islands near Guam from the Germans. When the US declared war on Germany in 1917 the SMS Cormoran was scuttled in about 120ft of water in Apra Harbor where it sits today.

That digression is just to say; yes the Japanese were active in searching for Germany's East Asian Squadron and helping to neutralize the German possessions in China. They were also very interested in acquiring Germany's colonial possessions in the Pacific.

Certainly the capture of Germany's possessions in Micronesia helped feed into the tensions that would boil over in the Second World War. Japan's action seizing the islands was not pre-approved by the allied forces and was only recognized after the war by the League of Nations. Japan's new colonies became known as the Japanese South Pacific Mandate. While the population of the islands at this time was at a historic low point and the economy was based around a single export product: copra (though there was phosphate mining on Anguar); the Japanese were keen to use the islands for Japanese settlement. Japan invested a great deal in building infrastructure on the islands and importing Japanese farmers. Japan also closed the islands to outsiders, likely in the hope of keeping the fortifications they were building on the down low.

A good book on this topic is "Nanyo" by Mark Peattie which traces the whole history of Japanese involvement in the South Seas from 1885 to WW2.

edited spelling

This is quite a broad question, so I will just go through a quick summary of Japan's contributions. If you have more specific questions feel free to ask.

Japan joined the side of the Entente Powers (note, not called the "Allies" or "Allied side") in 1914. Their main land contribution to the war effort was seizing German leased territory in China (such as Tsingtao, which the laid siege to in 1914) and seizing a number of German colonies in the Pacific.

When the war started the Germans had a number of naval vessels in the pacific, and the Japanese navy assisted in patrols to find these (though I do not believe they were engaged in combat). They also send 4 destroyers to the Mediterranean in 1917 to assist with anti-submarine patrols.

Following the collapse of Imperial Russia the Japanese sent troops into Siberia to assist the White Russian troops fighting the Bolsheviks (alongside the US who, despite having less than stellar relations with Japan, now found themselves on the same "team").