Japan was part of the Axis.
Japan had begun an invasion of China in the 1930's, and established some puppet states, such as Manchuria.
Signatory to the Axis treaty, Japan claimed the French Indochine (as Protector to Vichy France), and the Netherland East Indies (as protector to the Reich Provisional Government in Netherlands), however Britain contested those claims, while taking effective control of the Netherland East Indies in the name of the Netherland government in exile. Japan declared war to Britain seizing British interests in China. When Britain begun Soviet campaign, reach an agreement with Japan. Britain would keep protectorate status on Netherlands East Indies and Japan would respect British interest in China and Southwest Asia, as well as Free France and American interests in China, while Britain would supply Japan with oil and coal, and Britain would not contest any advance Japan would attempt in the Soviet Union.
When Germany officially declared war to the Soviet Union, so did Japan, and begun an invasion of the Soviet Union, opening a eastern front.
At the defeat of the Soviet Union in 1944, Japan claimed all occupied territory, supported by both Britain and Germany. The new Russian government manage to negotiate that Vladivostok would be preserved in Russian hands, and Japan allowed a corridor from Central Siberia to Vladivostok.
The Japanese war in China continued, however, and in 1948, Japan had effective control of all Northern China and the main port cities in southern China. Japan had stood to the agreement of not interfering with commercial interests of the western powers.
In 1949, Japan established a puppet regime in Indochina, approved by Germany and without consulting the French collaborationist government.