Japan was known about in Europe from the voyages of Marco Polo (1254-1324) who called it Cipangu and reported it as 1500 miles east of the Chinese coast and having abundant gold. It was to find a westerly sea-passage to Cipangu and Cathay (China) that Columbus set sail in 1492, only to discover that America lay in his path. The first European contact by sea with Japan was made by the Portuguese for whom Vasco da Gama established the first trading post on the Indian sub-continent in 1511, enabling the Portuguese to build an extensive maritime trading network in south-east Asia. It was from Goa that they began to trade with Cochin China (Vietnam) in 1540 and reached Japan in 1543.
The first extended European mission to Japan …
Editors, Litencyc. "First European contact with Japan". The Literary Encyclopedia. First published 13 September 2005
[https://www.litencyc.com/php/stopics.php?rec=true&UID=1585, accessed 26 May 2019.]