 Just about every supermarket and convenience store sells them, not to mention train station kiosks, vending machines and more. They are as common as pre-made sandwiches are in the West. (Actually you can get pre-made sandwiches as easily too in Japan.)  Just about every supermarket and convenience store sells them, not to mention train station kiosks, vending machines and more. They are as common as pre-made sandwiches are in the West. (Actually you can get pre-made sandwiches as easily too in Japan.) 