This rice ball recipe is an Okinawan food with a strong Western influence. Pork luncheon meat such as the SPAM or TULIP brands are easy to find in Okinawa because of the large presence of Americans in the area. Although you can find this onigiri in other places in Japan, you can not find it as common as it is sold in Okinawa. This is a special type of onigiri because the shape is rectangular as opposed to the usual triangular shape of a rice ball. The ingredients used to make this rice ball are easy to find so you can make it anywhere.