There certainly were a number of patriotic songs sung by Japanese children during the war, and there were probably similar songs being sung by children in all the combatant countries. A domestic population's natural and very strong instinct is to support the cause and serve and defend the nation to the utmost. In the case of aggressor countries who start wars, it is almost never clear to most of the domestic population that their own government is the aggressor and is in the wrong.

The Japanese population, for instance, was under the understanding that China had started the war with Japan in the late 30's (actually, the Japanese troops started it by attacking China at the Marco Polo Bridge), and that the USA was assisting China and cutting off Japan's supplies of oil and steel (which was, in fact, true...but the Americans and Chinese didn't see that as a bad thing, needless to say). Therefore, the Japanese citizens and their leaders must have felt that Japan had every good reason to go to war with the USA...and was justified in doing so. This necessitated a pre-emptive attack on Pearl Harbour. The USA made a "pre-emptive attack" on Iraq in 2003...remember? Not being in any real danger from the Iraqi military, however, the USA could do it openly. The Japanese had to do it by stealth, because they were facing an enemy with similar military capability to their own...and far greater resources.

Similarly to the Japanese, the German people were under the impression that the Poles were responsible for the war with Poland in 1939, and that the French and British were responsible for widening that war into a world war by declaring war on Germany! Thus, they would have seen Germany as the victim of foreign aggression and betrayal.

It's always "the other guy" who is seen as being at fault, right? ;-) Governments are quite good at getting their populace to support a war they have planned on and chosen...they just point the finger at a danger supposedly posed by "the other guy", and the people believe it.