We think of Japan as a single island, but it actually is four large islands and thousands of smaller ones. The volcanic and mountainous terrain boasts lush forests and heavy rainfall, much of it from monsoons, and the scarce farm land is used predominantly for rice. As one would expect, fish plays a major dietary role, both fresh and preserved.
In the third century BC, Korea's already developed rice growing techniques were passed to the Japanese by the Yayoi, a migrating tribe that settled in Japan. Rice came to be used for more than eating, including paper, fuel, wine, building materials and animal feed.
During the development of Japan, the Chinese contributed soy sauce, tea, chopsticks and imperial rule. Other influences arrived in Japan via Korea, including Buddhism, which, despite the pre-existing Shinto and Confucian religions, became the official religion in the sixth century. For the next 1200 years, meat was officially forbidden to the Japanese people.
Then in the sixteenth century the Portuguese, followed by the Dutch, came looking to corner the trade market with Japan. The westerners introduced fried foods, which is why the breaded, fried tempura seem so very un-Japanese; while the Japanese enjoyed this type of cooking, it was not something that evolved naturally. Tobacco, sugar and corn were also brought by the traders.
Around 1600 (and lasting until 1868), Japan's shogun Tokugawa Ieyasu (of James Clavell's famous novel, "Shogun") feared the Europeans would spark great wars; so he closed the ports and expunged the foreigners. During this period of isolationism, Japan's culture became even more deeply rooted. The main religions of Buddhism and Shinto emphasize the seasons and this came to be reflected in the foods served. In fact, it is because of Buddhism that meals feature five flavors and colors, respectively being: sweet, spicy, salty, bitter and sour; and yellow, black, white, green, and red.
US Commodore Perry forced the Japanese to renew trade with the West in 1854, and soon a new Japanese ruling order took power. Interestingly, the new Emperor Meiji staged a New Year's feast in 1872 designed to embrace the Western world; it was completely European in detail and for the first time in over a thousand years, the people publicly ate meat.