Onigiri is made from white rice formed into triangular or oval shape and often wrapped in nori seaweed. Traditionally, an onigiri is filled with umeboshi, salted salmon, katsuobushi, or any other salty or sour ingredient as a preservative. Onigiri is not a form of sushi, despite a common misconception. While onigiri is made with plain rice (perhaps lightly salted), sushi is made of rice with sugar and vinegar added. Onigiri makes rice portable and easy to eat as well as preserving it, while sushi originated as a way of preserving fish.
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