Hi Miki
Ask me!! A hardcore veggie whos been to Japan a few times.
The only Japanese who would be veggies, would be the Buddhist monks, I guess.
Japanese food, almost EVERYTHING, has fish powder in it. Even if you ask for plain soba (buckwheat noodles), it would have fish powder in it.
If you are going to Tokyo, you can survive. There are chains like subway, Quiznos etc where you can get cheese sandwiches, burgers etc.
If you like Indian food, there are many Indian restaurants in Tokyo.(expensive though, almost twice the cost of Japanese meal)
If you landup in ,say, Denny's, again a chain of restaurants open 24 hours, then you will need to order whatever you want to, and request the waiter to make it without fish and meat. (Remember, just saying 'meat' won't suffice).
In Pizza hut etc, there are some veggie pizzas available (though pretty expensive)
Wherever you may go in Japan, even if the food appears harmlessly veggie, there is an extremely HIGH probability that it has meat/fish related stuff in it.
But all in all, there is nothing more painful to a veggie in Japan than the food .
I love Japan and all Japanese related stuff, but no, not the food! Its so difficult to adjust'ne.........:-((
Sorry to be negative, but be prepared in case you reach there!!!