Onigiri has an ancient history. During the Heian period (794-1185), rice balls called tonjiki were eaten during picnics and travel.
Onigiri were used as provisions for troops in the 16th century and have been carried on trips and picnics to this day, traditionally filled with umeboshi, whose antibacterial properties help keep the rice fresh.
Originally, onigiri were often wrapped in dry bamboo leaves to handle them while traveling; the practice of covering them with dried nori began in the mid-19th century.
The latest onigiri trend is onigirazu, a hybrid of onigiri and sandwich, whose origins came from a manga comic. Unlike traditional onigiri, onigirazu is not compressed or shaped by hand, making it somewhat easier to prepare. Its fusion-style fillings are based purely on personal taste: warm rice is spread over a sheet of nori, then layered with unexpected ingredients such as ham and cheese, sautéed shrimp in chili sauce, salmon and cream cheese, or omelet and bacon.
The nori is then folded into a square around the rice, and sliced in half like a sandwich. Not only is it simple and fun to make, but onigirazu is visually appealing and allows for large fillings that would not typically fit inside a regular onigiri.
