Long story short
The history of sushi began around the 8th century in Japan. The original type of sushi was first developed in Southeast
Asia as a means of preserving fish in fermented rice. In the Muromachi period, people began to eat the rice as well
as the fish. During the Edo period, vinegar rather than lacto-fermentation was used to sour the rice. In modern times,
it is an early form of fast food strongly associated with Japanese culture.
For almost the next 800 years, until the early 19th century, sushi slowly changed and the Japanese cuisine changed as well. The Japanese started eating three meals a day, rice was boiled instead of steamed, and of large importance, was the development of rice vinegar. While sushi continued to be produced by fermentation of fish with rice, the addition of rice vinegar greatly reduced the time of fermentation and the rice used began to be eaten along with the fish. In the Muromachi Period (1336 to 1573), the process of producing Oshizushi was gradually developed where in the fermentation process was abandoned and vinegar was used. In the Azuchi-Momoyama period (1573–1603), namanare was invented. A 1603 Japanese-Portuguese dictionary has an entry for namanrina sushi, literally half-made sushi. The namanare was fermented for a shorter period than the narezushi and possibly marinated with rice vinegar. It still had the distinctive smell of narezushi.