A document records that Kiei SO (宋希景), a kaireishi (an officer sent to Japan responding to an envoy sent by Japan) sent to Japan in 1420, gave an exclamation of surprise about the highly progressed monetary economy that even a beggar wanted money instead of food (this was because, in Korea at that time, paper money called Choka was circulated only in urban areas, with no system that could be called a monetary economy established yet, and the economy was centered on barter trade based on the media of rice and cloth), and in addition, it is likely that the envoy from Korea brought back products of culture necessary for them, such as sweet potato that rescued Korean people from a famine in Korea in later years (1764) and water-pumping wheels.
1420年の回礼使である宋希景は乞食が食物ではなく銭を欲しがるような貨幣経済の発達に対して驚きの声を上げた（その時の李氏朝鮮では、都市部で楮貨という紙幣が流通していた程度で、貨幣経済と呼ぶに足るものが成立しておらず、布・米を媒体とした物々交換が主であったため）といった記録が残っており、また、朝鮮で後に飢饉を救ったサツマイモ（宝暦度1764年（宝暦14年））や揚水式水車など、日本から相応の文物を持ち帰っていたようである。