Leaders in china and japan decide to cut off contact with other contries, explain why they close there borders and turned inward ( i need )

Stop begging, but the answer is What Prompted the End of the Treasure Fleet?

In part, the sense of surprise and even bewilderment that the Ming government's decision elicits in western observers arises from a misunderstanding about the original purpose of Zheng He's voyages. Less than a century later, in 1497, the Portuguese explorer Vasco da Gama traveled to some of the same places from the west; he also called in at the ports of East Africa, and then headed to India, the reverse of the Chinese itinerary. Da Gama went in search of adventure and trade, so many westerners assume that the same motives inspired Zheng He's trips.

However, the Ming admiral and his treasure fleet were not engaged in a voyage of exploration, for one simple reason: the Chinese already knew about the ports and countries around the Indian Ocean. Indeed, both Zheng He's father and grandfather used the honorific hajji, an indication that they had performed their ritual pilgrimage to Mecca, on the Arabian Peninsula. Zheng He was not sailing off into the unknown

Explanation:

demand is the need and oportunity to buy a given good or service.