Define warrior society. Japan had not been at constant war for hundreds of years. In fact, prior to Japan's discovery of the West, many Japanese students studied in China to acquire its knowledge. It had been influenced by Chinese Confucianism and Buddhism, both of which taught morals and ethics. Many Chinese works had been translated into Japanese. And Japan traded extensively with Korea, which in turn traded with China, which in its turn was linked to the Silk Route. Japan was not exactly a rabid and closed-minded society throughout its existence. The fact that it did allow itself to be so influenced from abroad, including the West, shows how open a society it was. Just read up on Nitobe Inazo, Hasegawa Teru, the Oomoto religion, etc. to see how Japan had progressive influences even in modern times, just prior to, even during, and still after WWII.
Through industrialization, progress and material advancement got the best of the Japanese ego, unfortunately, as it thought of itself as suddenly superior to its neighbours who were previously more advanced than Japan, and so felt that it needed an empire of its own to match the others world empires.
But to portray Japanese culture as intrinsically militaristic seems false, looking at the history of its openness to outside influences.