Actually, in 1540's, Christian missionaries with Francis Xavier arrived in Japan at all risks and briefly spread the religious mainly in Kyushu area. He was the first Jesuit to go to Japan as a missionary. At first, Jesuits were supported by the shogunate, thinking that they would reduce the power of the Buddhist monks and help trade with Spain and Portugal. Everything from Western countries should had been novel and strange for Japanese people. The Jesuits believed that it was better to seek to influence people in power and then allow Christianity to be passed downwards to the commoners later. As a result, several daimyo (powerful Japanese feudal lords) became Christians, soon to be followed by many of their subjects. There was a commercial and political merit to become Christians for them, in order to gain more favourable access to gunpowder. At the same time the missionaries faced the hostility of many other daimyōs.
Since 1565, edicts to ban Catholicism had been issued. Yet, overall, remarkably strict policies toward Catholicism hadn't been undertaken due to the need to gain a profit from trade. In 1600 Tokugawa Ieyasu assumed power over Japan. He disliked Christian activities in Japan. The shogunate was increasingly concerned and wary of colonialism seeing that the Spanish had taken power in the Philippines after converting the population, and also fed distrust against Christian daimyos' movements. And he finally decided to ban Catholicism on 1612 and 1613.
In 1637, the Shimabara Rebellion erupted in Nagasaki Prefecture (in Kyusyu). It was largely rebellion involving peasants, against tax hike for clan's construction of a new castle. And also religious persecution of the local Catholics exacerbated the discontent provoked anger from them. Most of peasants were Catholics. A charismatic 16-year-old boy, Amakusa Shiro was chosen as the rebellion's leader, like Japanese Jeanne d'Arc, and entrenched themselves in Hara Castle. Eventually, the Tokugawa Shogunate sent a force of over 125,000 troops to suppress the rebels and, after a lengthy siege against the rebels at Hara Castle, defeated them by ruthless and violent way. Amakusa Shiro was beheaded and the prohibition of Christianity was strictly enforced. Some people think that it was sort of religious war in Japan.
In the mid-17th century, the shogunate demanded the expulsion of all European missionaries and the execution of all converts. At that time, most Japanese Christians lived in Kyushu area, but Christianization had already a national impact. It is said that by the end of the 16th century it was possible to find baptized people in virtually every province of Japan.
In my hometown Sendai, daimyo Masamune Date (1567-1636) had ruled the land, and expanded trade in the remote, backwater Tōhoku region. He was an aggressive and ambitious man, and sympathized with foreign causes. He is known to have encouraged foreigners to come to his land. Also He funded and promoted an envoy to establish relations with the Pope in Rome, and sent Hasekura Tsunenaga (1571-1622) and others from port of Ishinomaki, Miyagi to Spain and the Vatican in Rome as a diplomatic mission in the years 1613 through 1620.
When the Tokugawa government banned Christianity, Masamune, though disliking it, had to obey the law, and let Tokugawa persecute Christians in his domain. It is said his anti-Christian measures were comparatively mild. (Some sources suggest that Masamune's eldest daughter was a Christian).
By the time Tsunenaga came back, Japan had changed quite drastically; an effort to eradicate Christianity had been under way and Japan was moving towards the 'Sakoku' policy of isolation. This expedition visited such places as the Philippines, Mexico, Spain and Rome. They met the King of Spain, but mission was failed because such negative news had already arrived in Europe. Hopes of trade with Spain evaporated as long as persecutions were occurring in Japan. But at least five members of the expedition stayed in Coria (Seville) of Spain to avoid the persecution of Christians in Japan. And their descendants with the surname Japón (Japan) are now living in Spain.
What became of Stunenaga is unknown and accounts of his last years are numerous. But it is said that the truth of his descendants and servants were later executed for being Christians, suggests that he remained strongly Christian. In the end, Date Masamune suddenly chose to distance himself from the Western faith.
I am sure Masamune had an ambition to dominate the whole country too. He just found few opportunities to move forward at the time. I think he had a good foresight but always were hampered by resistance from others. We also visited Sendai City Museum again, where painting, letter and others from Europe display, which Tsunenaga brought back to Sendai. It was a good opportunity to visit a historical place in my hometown and learn local history not only fragmentary but also in conjunction with whole Japanese historical movement.