I think you need to have an address in Japan to apply for one.
but the price there is already quite good. do check out for the toys, I remember buying some really nice toys for a good price, especially if you like Hello Kitty ones.
if you need baby stuffs, check out the car seats and strollers, very good price if you are not looking for the latest models. do check on the internet and plan how much money you need to bring there because you need to pay in cash, they don't accept visa/jcb cards.