I've never been to japan, only to Taiwan, but they used to eat Ramen and Sushi and other things. Ramen is sth. I consider very Japanese and I tried to make my own recipes from here: http://japanesefood.about.com/cs/noodles/a/ramen.htm
I'm pretty sure they have otehr great food too, but they even made a movie about Ramen in Japan (the Ramen girl with brittany murphy). It has a very long tradition in Japan :)
Sushi is the best. I have never been to Japan but sometimes my friends took me to Japanese restaurants and their food is wonderful. Besides sushi, I also like Tempura and Goudon (not sure if I spell it right) :)