Onigiri , also known as omusubi (お結び), nigirimeshi (握り飯), or rice ball, is a Japanese food made from white rice formed into triangular or cylindrical shapes and often wrapped in nori. Traditionally, an onigiri is filled with pickled ume (umeboshi), salted salmon, katsuobushi, kombu, tarako, mentaiko, takanazuke or any other salty or sour ingredient as a natural preservative. Because it is easily portable and eaten by hand, onigiri has been used as portable food or bento from ancient times to the present day. Originally, it was used as a way to use and store left-over rice, but it later became a regular meal. Many Japanese convenience stores and supermarkets stock their onigiri with various fillings and flavors. It has become so mainstream that it is even served in izakayas and sit-down restaurants. There are even specialized shops which only sell onigiri to take out. Due to the popularity of this trend in Japan, onigiri has become a popular staple in Japanese restaurants worldwide.

Nori (海苔) is a dried edible seaweed used in Japanese cuisine, usually made from species of the red algae genus Pyropia, including P. yezoensis and P. tenera. It has a strong and distinctive flavor, and is generally made into flat sheets and used to wrap rolls of sushi or onigiri.