Sushi and sauerkraut are pickled foods. In 200 AD, that is, in the post-Han era, China has begun to spread the food "sushi", which is interpreted in the dictionary as food made of salt, vinegar, rice and fish fillets. During the Song Dynasty, there were frequent wars in China. Sushi was only the food of refugees, with more varieties, including vegetables, fish, meat and even shellfish. In 700 AD, in the Nara era, Japanese businessmen who went abroad for business spread sushi to Japan. At that time, the Japanese used some vinegar-soaked rice balls and some seafood or meat, pressed them into small pieces and arranged them neatly in a small wooden box as food along the way. It was not until A.D. 1700, that is, the Edo period, that sushi was widely circulated in Japan and became an ordinary food.