Your Visa card is widely accepted throughout Japan (although you might need to let the cashiers swipe it for you). In the event of a lost or damaged card, you could get an emergency replacement in as fast as 24–72 hours.
Keep in mind that on the JR (Japan Railway), you have to go to the ticket counter to use your overseas-issued Visa. Also, not all merchants who accept Visa display the Visa acceptance signage, so make sure to ask.
Need cash in Japan? Many shops in restaurants in Japan do not accept cards, so it’s a good idea to carry cash with you. With ATMs available throughout Japan there is no need to get local currency before you travel. Getting cash at your destination should be easy, safe, and getting cash at an ATM can actually be less expensive.