After the Portuguese first made contact with Japan in 1543, a large scale slave trade developed in which Portuguese purchased Japanese as slaves in Japan and sold them to various locations overseas, including Portugal itself, throughout the sixteenth and seventeenth centuries. Many documents mention the large slave trade along with protests against the enslavement of Japanese. Japanese slaves are believed to be the first of their nation to end up in Europe, and the Portuguese purchased large numbers of Japanese slave girls to bring to Portugal for sexual purposes, as noted by the Church in 1555. King Sebastian feared that it was having a negative effect on Catholic proselytization since the slave trade in Japanese was growing to massive proporations, so he commanded that it be banned in 1571.

Japanese slave women were even sold as concubines to black African crewmembers, along with their European counterparts serving on Portuguese ships trading in Japan, as mentioned by Luis Cerqueira, a Portuguese Jesuit, in a 1598 document. Japanese slaves were brought by the Portuguese to Macau, where some of them not only ended up being enslaved to Portuguese, but as slaves to other slaves, with the Portuguese owning Malay and African slaves, who in turn owned Japanese slaves of their own.

Toyotomi Hideyoshi was so disgusted that his own Japanese people were being sold en masse into slavery on Kyushu, that he wrote a letter to Jesuit Vice-Provincial Gaspar Coelho on 24 July 1587 to demand the Portuguese, Siamese (Thai), and Cambodians stop purchasing and enslaving Japanese and return Japanese slaves who ended up as far as India. Toyotomi blamed the Portuguese and Jesuits for this slave trade and banned Christian proselytizing as a result.

Some Korean slaves were bought by the Portuguese and brought back to Portugal from Japan, where they had been among the tens of thousands of Korean prisoners of war transported to Japan during theJapanese invasions of Korea (1592–98).^[18][19] Historians pointed out that at the same time Hideyoshi expressed his indignation and outrage at the Portuguese trade in Japanese slaves, he himself was engaging in a mass slave trade of Korean prisoners of war in Japan.

Fillippo Sassetti saw some Chinese and Japanese slaves in Lisbon among the large slave community in 1578, although most of the slaves were blacks.

The Portuguese “highly regarded” Asian slaves like Chinese and Japanese much more “than slaves from sub-Saharan Africa”. The Portuguese attributed qualities like intelligence and industriousness to Chinese and Japanese slaves which is why they favored them more.

In 1595 a law was passed by Portugal banning the selling and buying of Chinese and Japanese slaves.