[samurai007]

Are you going on the JET program, or do you have another job? If so, after the 1st month, your salary should suffice, rather than your credit card. I never used my credit card there, I took traveler's checks for the 1st month. Most places won't accept credit cards, and I never used to ATMs there for anything other than withdrawing cash from my account, so I have no idea about credit card charges there. You could simply take cash if you want, Japan is very safe, but Traveler's checks would be safer.

Most restaurants aren't going to have vegan food. If you say "no meat", they'll usually still think fish, eggs, milk, etc are ok. Some monks are vegetarian or vegan, you might try to befriend them and ask if they know any places to eat that do it. Otherwise, cooking for yourself is the best way to be sure, if it's important to you.