Sushi began centuries ago in Japan as a method of preserving fish by fermentation. It is said that Sushi originated in Southeast Asia between the first and second century. The mountain people of that region preserved fish meat by storing it with rice and salt. Cleaned and gutted raw fish were placed between layers of salt and rice and pressed by a heavy stone. The natural fermentation of rice produced lactic acid that helped preserve the fish. After a few weeks, the stone was removed and a few months after that, the fermented fish were ready to eat. In those days, only the fish meat was eaten and the rice was discarded. Even today you find fermented fish meat called "Pra Som" (sour fish) in the northern part of Thailand.

This preservation method of food was introduced into China then into Japan. It came to Japan before 800 A.D. and eventually took form as NAREZUSHI. One of the best known NAREZUSHI today is called "Funa-sushi" in Shiga Prefecture, which is made with freshwater carp and dates back 1300 years. Preparing NAREZUSHI takes from 2 months to more than a year.

In the 15th century, people shorten fermentation time (half a month to one month) and began to eat preserved fish meat with rice that was used for the fermentation. Because the fish meat was not completely fermented and still somewhat raw, this was called NAMANARE (semi-fermented). This movement of eating the rice and not discarding it began mainly because rice was still a very precious item for the commonalty and people were hesitant about discarding it.

In the middle of 17th century, rice vinegar was used in Sushi making for the first time. Matsumoto Yoshichi, a doctor in Edo, hit upon the idea of adding vinegar to rice in Sushi making. The resulting tartness was gratifying even without fermentation, and the time it was necessary to wait before eating the Sushi was substantially reduced. This is called HAYAZUSHI (instantly prepared Sushi). This was the beginning of Sushi rice. After this breakthrough, Sushi was no longer a preserved food, instead it was reborn as an instantly-prepared food.

After the introduction of Sushi rice, variations of Sushi started to emerge. For example, SUGATAZUSHI (Fish stuffed with Sushi rice), and KOKERAZUSHI (Boxed Sushi). Because KOKERAZUSHI used to be one large piece of Sushi that needed to be cut to eat, people started to insert bamboo leaves to divide it into small pieces.

By the mid 18th century, MAKIZUSHI (Sushi rice, vegetables and fish wrapped with Nori seaweed), INARIZUSHI (Fried bean curd stuffed with Sushi rice), and CHIRASHIZUSHI (Sushi rice placed in a bowl and topped with various kinds of fish) were introduced.

By the early 19th century, NIGIRIZUSHI, the form of Sushi most commonly known among Westerners today, made its debut. In 1824 a man named Hanaya Yohei conceived of the idea of sliced, raw fish and other seafood at its freshest, served on small handful of vinegared rice. The stall he opened in the bustling Ryogoku district of Edo (old name for Tokyo) caught on at once. The squeezing method of Yohei was much like the one in use today. His sushi was prepared and served for customers on the spot at his Sushi stall. Much like today's hot dog stands, customers stood in front of the stall, picked up Sushi in fingers and popped it into mouth. The ease and quickness must have agreed with rather fast-pace quick-temper Edoites. In the middle of the 19th century, Sushi stalls began emerging all over Edo. They were patronized until after World War II when they ware banned.

There are two distinct styles in Sushi; Tokyo style and Osaka style. NIGIRIZUSHI (Tokyo style) is often referred to as Edomae-sushi. Edomae literally means "in front of Edo" and in front of Edo is Tokyo Bay, whose waters used to be rich with fish and seafood for Sushi making. For this, Edoites had an advantage over people in other regions. NIGIRIZUSHI is by far the mainstream of Sushi around the world. In Osaka, a city in western Japan, there is still an elaborated tradition of Sushi pressed with rice in wooden boxes. This type of Sushi is called HAKOZUSHI (Boxed Sushi). Osaka has always been the commercial capital of Japan and the rice merchants there developed Sushi that consisted primarily of seasoned rice mixed with other ingredients and formed into decorative packages.

Reference:
“Sushi: From preserved food to instantly prepared food” (Serai magazine) by Terutoshi Hibino
“Why Osaka’s HAKOZUSHI did not gain nation-wide popularity?” (Serai magazine) by Naomichi Ishige

A few faux pas in Sushi dining may be overlooked in most western establishments because it is not expected of Westerners to know all the rules (and don't expect all Japenese people to know all the fastidious rules!). Here are some of the basics that are certainly worth remembering and you may want to try next time.

Sushi is a finger food. Don't shy away from picking up Sushi with your fingers.

Originally Sushi was eaten without dipping into soy sauce. If soy sauce is needed, dip on the topping side, NOT on the rice. Pick up Sushi in your fingers, turn it over and lightly dip the fish in the soy sauce. If you dip Sushi into the soy sauce rice-side-down and let it soak up into the rice, Sushi disintegrates leaving little soy-stained rice all over the table. Japanese people rarely have this problem, because they know that the purpose of the soy is not to flavor the rice, but the fish. As such, the Sushi should be dipped rice-side-up in the soy sauce and then carried to the mouth.

Do not bite off a piece and put the remainder back on the plate. Pop the whole thing into your mouth.

Do not pour soy sauce into the soy sauce dish to the brim. Pour about one or two table-spoon of soy sauce at a time and pour it again after you used it all. This also prevents you from splashing it on the table. Traditionally soy sauce is considered as very precious item in Japanese culinary culture, so when you finished the meal, all the soy sauce you poured into the dish should be used up.

Do not mix Wasabi into soy sauce. Wasabi is already placed in Sushi between fish and rice by the chef. If you like it extra hot, ask the chef for extra Wasabi when you order it.

When not using your chopsticks, you should place them in front of you, parallel to the edge of the Sushi bar, with the narrow ends in the provided hashi oki if available; never place them directly on the bar.

Never leave rice after a meal. Leaving any kind of food is considered rude, but leaving rice is especially so. Leaving even a single grain of rice in the soy sauce dish or on the Sushi bar is considered as unrefined manners.

But of course...
you can alwasy forget all this fussiness and simply enjoy yummy sushi