aww dont worry too much - japanese food isnt as narrow variety as we see here
Im like you; im vegetarien ; no meat at all and no fish! also im picky about what vegetables i eat!
i didnt have too much of a problem finding food in japan; as i said theres alot more variety over there than what we see in resurants over here.
you'll find that there are actually alot of japanese food that will cater to your tastes; beef is very popular in japan
also there are more forien resurants in tokyo especially - so no problems finding food to your own tastes - we found a pancake house in harajuku and a indian in roppongi ^^
as for trying things over here....
try vegetarien sushi (i love it) and also you can get beef sushi
vegetable terriyaki (cant spell TT_TT)
umm i had more ideas but i forgot, sorry!
miso is an aquired taste, but it does grow on you!
(i like it now - i also didnt at first)
hope that was helpful; good luck! ^^