Although imperialism ended up hurting the Japanese people tremendously by involving them in World War II, it was beneficial to them for a while before the war. This, of course, ignores the harm that was done to many people in the areas that the Japanese took as an empire.
For Japan, the benefits were largely the same as the benefits of imperialism for any other nation. Imperialism allowed Japan access to more raw materials than it had on its own home islands. Imperialism gained Japan territory to which some Japanese could move in search of better economic prospects. Imperialism helped to make Japan a world power. This last factor is particularly important for Japan since it had been a technologically backward country that was far behind the west. Japan was forced to “open” to the world in 1853 by superior Western technology. By 1905, Japan was able to defeat Russia in a war. This was beneficial to Japan psychologically because it convinced Japanese people that they were just as good as Westerners.