They lived there and still do so.
The Japanese called it a "sphere of influence". They wanted to totally dominate Asia and the Pacific Islands.
Australia's involvement in Asia was to provide help to the Allies and also to a couple of Asian armies so they can stop the Japanese advance and push the Japanese back to their country to end the war on the side of Asia.
The Japanese shared similar feelings to Hitler. Invade now, Think later. The Japanese wanted to invade the world with Hitler, so it would be common sense to think that they had a feeling of pure hatred toward the rest of Asia, and indeed the world.
They felt that they were superior and felt that they had the right to take over Asia to provide more resources for themselves.
They were doing their part in their alliance in the war.
Chuichi Nagumo
During World War II, Japanese controlled much of Southeast Asia from European nations. When the Japanese ruled the area, it showed them that Europeans were far from invincible. When the war ended, the Japanese left Southeast Asia. Europeans then wanted the land back. But many of the people of Southeast Asia did not want to live under the Europeans any longer. Southeast Asia eventually won independence and new nations were formed.
In World War I, the Japanese joined the Allies for a time, and fought the German army in east Asia.
The occupied Asian countries now had to provide labor to support the Japanese war machine.
Well, the involvement was that the entire area was invaded by Japan. Large portions of China and Korea were occupied by the Japanese. Many of the island nations, including the Philippines were invaded by the Japanese. In most cases large groups of natives worked with US and British forces to establish undergrounds and guerrilla forces to fight the Japanese.
The USA was controlled by the USA. Parts of Asia were overtaken by the Japanese and other parts were still self-controlled and battling the Japanese.
During World War II, the Japanese Empire expanded significantly, gaining control over territories in East and Southeast Asia, as well as parts of the Pacific. This expansion included countries such as Korea, Taiwan, parts of China, the Philippines, and various islands in the Pacific Ocean.