Maybe it has to do with their belief system. Shinto and Buddhism are Japan's two big religions, and I don't think either one places huge focus on materialism (which I suppose is one reason why people loot in a crises). I'm sure there are individuals that are as greedy as Gordon Gecko, but maybe not generally as a population.
Half of Japanese language is written using Chinese characters, Zen Buddhism originated from China and was brought to Japan. Entire culture especially the intelligentsia was heavily influenced by Confucianism. Karate also originated from China. "Karate began as a common fighting system known as te (Okinawan: ti) among the Pechin class of the Ryukyuans. After trade relationships were established with the Ming dynasty of China by King Satto of Chūzan in 1372, some forms of Chinese martial arts were introduced to the Ryukyu Islands by the visitors from China, particularly Fujian Province. A large group of Chinese families moved to Okinawa around 1392 for the purpose of cultural exchange, where they established the community of Kumemura and shared their knowledge of a wide variety of Chinese arts and sciences, including the Chinese martial arts." http://en.wikipedia.org/wiki/Karate
A humble observation: it takes an impressive imagination to be corrupt. Americans have great ingenuity.
There is a difference between looting water and food when you can't buy it and looting TVs and other unessential electronics equipment. Speaking with Japanese people, there is some looting as there was when the Great Hanshin (Kobe) earthquake happened, I heard that the Yakuza drove away the looters therefore winning the support of many people.
that may be, but I also wouldn't expect anyone is concerned about stealing their neighbors TV or sound system right now anyway since they are without power