Rice balls are a kind of traditional food in ancient China, which was popularized as military food in the Han Dynasty and later spread to Japan. The main ingredient is rice and the main ingredient is fish fillets. Producers can add ingredients according to their own preferences, and they can also make rice balls of various styles according to their own preferences.

Rice balls have changed since the age of 1970. The traditional impression of rice balls is that in a fluffy white rice, the stuffing may be roasted salmon, and the whole rice ball is covered with seaweed by the mother. And convenience stores have completely changed this picture.