China had a serious, flourishing, cosmopolitan age with people from tens of unique cultures and simultaneously invented critical technologies such as printing.

China had a serious, flourishing, cosmopolitan age with people from tens of unique cultures and simultaneously invented critical technologies such as printing. Japan and Korea basically simply absorbed more from China, and there's little evidence that they came in to direct contact with foreigners from further afield such as Central and South Asians except inside of or via China. For example, the period Japanese monk Ennin records that he visited a certain monastery near Taishan, at which the graves of numerous South Asian monks (as well as some Koreans, etc.) are found. His motivation for travel was literally seeking knowledge, and his destination was China.