The earliest form of sushi, a dish today known as narezushi, has its probable origin with paddy fields along the Mekong river in Southeast Asia. The prototypical narezushi is made by lacto-fermenting fish with salt and rice in order to control putrefaction. Spreading southwards down the Mekong, narezushi then entered Austronesia. In Japan the dish's distribution overlaps with the introduction of wet-field rice cultivation during the Yayoi period.
Narezushi appears in the Chinese dictionary in the 2nd century AD as the character sa (鮓, pickled fish with salt and rice), which was during a period in which Han people were migrating south of the Yangtze river, adopting the food from the non-Han minority peoples.
The Japanese preferred to eat fish with rice, known as namanare or namanari (生成, なまなれ, なまなり, semi-fermented). During the Muromachi period namanare was the most popular type of sushi. Namanare was partly raw fish wrapped in rice, consumed fresh, before it changed flavor. This new way of consuming fish was no longer a form of preservation but rather a new dish in Japanese cuisine.
During the Edo period, a third type of sushi was introduced, haya-zushi (早寿司, 早ずし, fast sushi). Haya-zushi was assembled so that both rice and fish could be consumed at the same time, and the dish became unique to Japanese culture. It was the first time that rice was not being used for fermentation. Rice was now mixed with vinegar, with fish, vegetables and dried food stuff added. This type of sushi is still very popular today. Each region utilizes local flavors to produce a variety of sushi that has been passed down for many generations.
Today's style of nigirizushi (握り寿司), consisting of an oblong mound of rice with a slice of fish draped over it, became popular in Edo (contemporary Tokyo) in the 1820s or 1830s. One common story of nigirizushi's origins is of the chef Hanaya Yohei (1799-1858), who invented or perfected the technique in 1824 at his shop in Ryōgoku. After the Great Kanto earthquake in 1923, nigirizushi chefs were displaced from Edo throughout Japan, popularizing the dish throughout the country.