History of Roman Catholicism in Japan

Christian missionaries arrived with Francis Xavier and the Jesuits in the 1540s and briefly flourished, with over 100,000 converts, including many daimyo in Kyushu. It soon met resistance from the highest office holders of Japan. Emperor Ogimachi issued edicts to ban Catholicism in 1565 and 1568, but to little effect. Beginning in 1587 with imperial regent Toyotomi Hideyoshis ban on Jesuit missionaries Christianity was repressed as a threat to national unity. After the Tokugawa shogunate banned Christianity in 1620 it ceased to exist publicly. Many Catholics went underground, becoming hidden Christians (隠れキリシタン, kakure kirishitan^?), while others lost their lives. Only after the Meiji Restoration was Christianity re-established in Japan.

Portuguese shipping arrived in Japan in 1543, and Catholic missionary activities in Japan began in earnest around 1549, performed in the main by Portuguese-sponsored Jesuits until Spanish-sponsored Franciscans and Dominicans gained access to Japan. Of the 95 Jesuits who worked in Japan up to 1600, 57 were Portuguese, 20 were Spaniards and 18 Italian. Francisco Xavier, Cosme de Torres (a Jesuit priest) and Father John Fernandes were the first who arrived in Kagoshima with hopes to bring Christianity and Catholicism to Japan.

The main goal was to save souls for God. But religion was also an integral part of the state and evangelization was seen as having both secular and spiritual benefits for both Portugal and Spain. Wherever these powers attempted to expand their territories or influence, missionaries would soon follow. By the Treaty of Tordesillas, the two powers divided the world between them into exclusive spheres of influence, trade and colonization. Although at the time of the demarcation, neither nation had any direct contact with Japan, that nation fell into the sphere of the Portuguese.

...
Wikipedia