Japanese portolan sailing map, depicting the Indian Ocean and the East Asian coast, early 17th century. A portolan (derived from the Latin word portus, port is an early modern European navigation chart, dating from the Thirteenth century or later The Indian Ocean is the third largest of the world's Oceanic divisions covering about 20% of the water on the Earth 's surface
The crew of the red seal ships were international, for many Chinese, Portuguese, and Dutch pilots and interpreters joined the sails. The first Red Seal ships were required to have a Portuguese pilot on board, although the Japanese progressively developed pilots of their own. The Portolan maps used on the Red Seal ships were drawn on the Portuguese model, with directions in the Japanese language. A portolan (derived from the Latin word portus, port is an early modern European navigation chart, dating from the Thirteenth century or later
Major Southeast Asian ports, including Spanish Manila, Vietnamese Hoi An, Siamese Ayutthaya, Malay Pattani, welcomed the Japanese merchant ships, and many Japanese settled in these ports, forming small Japanese enclaves. The City of Manila Hội An is a small city on the coast of the South China Sea in the South Central Coast of Vietnam. Ayutthaya (full name Phra Nakhon Si Ayutthaya, พระนครศรีอยุธยา aˡjutʰajaː also spelled "Ayudhya" city is the capital of Pattani ( Thai ปัตตานี is one of the southern provinces ( changwat) of Thailand.
The Japanese seem to have been feared throughout Asian countries:
"The Japons are not suffered to land in any port in India (Asia) with weapons; being accounted a people so desperate and daring, that they are feared in all places where they come" (Sir Edward Michelbourne, Boxer, p268).