Sushi was originally served standing as a quick lunch. Try it out. Here is a history write-up by Kotaku.

Sushi itself has its roots in a dish imported during from ancient China, in which fish was salted and then wrapped with fermented rice to keep it from going bad. The fish could be preserved for months and when eaten, the fermented rice was pitched.  However, by the Edo Period (1603-1868), Japan had its own special spin on this meal by creating a type of sushi, known as haya-zushi, that was made so that the fish and the rice were eaten at the same time.

During the 18th century, Edo (present day Tokyo) experienced a boom in food stalls, which were akin to modern fast food restaurants. As part of the expanding take-out menu, nigiri-zushi was invented, appearing during the first quarter of the 19th century.

Yohei Hanaya (1799 to 1858) gets credit as nigiri zushi’s inventor—even Japan’s largest vinegar maker, Mizkan, calls him the “father” of sushi. (Though, as Nihombashi Tokyopoints out, there were other nigiri-zushi chefs at that time.) After selling his sushi at street stalls, Hanaya established his own restaurant, known as “Yohei’s Sushi,” that specialized in hand-pressed sushi.

As The History of Nihonbashi Uogashi explains, during the early 19th century, Japanese people did not hold tuna in high regard. Today, of course, tuna (or maguro) is one of the most important fishes found in sushi. Since the fish was plentiful, Hanaya served it up, preparing it with soy sauce and helping kick off a tuna craze in Edo.

The visual beauty of nigiri-zushi, combined with its freshness and quick prep time, made it a hit. Hanaya’s sushi was close to what you’d find today. For example, besides hand-pressing the sushi, he also used a dab of wasabi and vinegared rice—practices that continue. Below is a 1877 drawing of Hanaya’s famous sushi. You can still find many of these types of nigiri-zushi at restaurants in Japan.

Hanaya’s sushi was so popular that soon others began borrowing his creation. While Hanaya is credited with one of Japan’s most iconic meals, the government didn’t initially recognize him or his creation.  http://kotaku.com/the-inventor-of-sushi-1683686290