Far from just Sushi and Tempura Japanese food is very diverse. There are thousands of dishes and regional varieties of Japanese food. It seems like every region of Japan is famous for some delicacy. For example, Osaka is famous for Okonomiyaki and Hokkaido is famous for delicious seafood. In fact, if you want to truly experience Japanese food you might have to travel to all 47 prefectures of Japan.
Japanese food served outside Japan tends to focus on Sushi, Tempura, Teriyaki Chicken etc... But Japanese people do not eat these foods too often. A typical person may only eat Sushi once a month or so. The quality of Japanese food outside Japan may be much lower as well. Japanese restaurants are renowned for their quality food and wonderful service.