What was Japan doing when Liu Bang founded the Han Dynasty?

Historical period of Japan: Yayoi period (やよぃじだぃ) 300 BC-250 AD. In the Yayoi period, that is, around the third century BC, Japan's primitive society, which developed slowly, suddenly became rich overnight and jumped into a brand-new agricultural society. Japanese archaeologists, through in-depth study of a large number of unearthed cultural relics and sites, believe that the leap in the Yayoi era lies in the immigration to China during the Qin and Han Dynasties. They brought the advanced farming civilization of the mainland and a brand-new atmosphere to the Japanese archipelago. With the arrival of immigrants, the Yayoi people moved from the wet and cold coastal areas to the vast plains, built dry houses and made beautiful linen clothes. After basically solving the problem of food and clothing, women began to enjoy more jewelry and other decorations than before. Such as bracelets and necklaces. With the rise of agricultural society, the role of men in tribes is prominent, their status is gradually improved, and primitive society is gradually transitioning to class society. The most obvious sign of this change is the change of tomb specifications and the number of funerary objects.