The popularity of sushi in Japan may have been associated with Buddhism.
Buddhism was imported in the 6th century AD, and quickly became one of the major religions. One of the rules of Buddhism was to restrain from eating meat, and fish was not counted as such.
From China, kombucha made its way to Japan (between 250 and 538).
A Korean doctor who reached Japan is believed to have cured the digestive problems of the emperor at the time with tea fermented with a special mushroom.
