I’ve been studying the very interesting history of Japan by a historian from Britain, Sir George Sansom, (1883-1965). He goes into quite a bit of detail about Japan’s relationship with foreign countries, specifically with the Russians, Chinese, Koreans, British, Dutch, and Portuguese.
The Tokugawa Shogunate (ruling military government) of Japan largely closed its seaports to foreign vessels from 1633 to 1833. They especially feared Portugal and Spain but admitted the British and Dutch to Nagasaki. And they had no problems with the Koreans or the Chinese with whom they traded. Japanese scholars thirsted for scientific and technical knowledge from the West that the Dutch brought them, but closed its ports to so called “Christian” missionaries.
And who were these missionaries? They were Jesuit priests, really soldiers and spies for Rome! Roman Catholic Portugal and Spain were under the control and influence of the Pope, but England and the Netherlands, being Protestant at the time, had broken free from Rome. According to George Sansom, the seclusion policy meant to “resist the pressure of Christian propaganda” but in my opinion, the reason for the policy was more to thwart the threat of invasion and colonization by Roman Catholic countries controlled by the Pope.
The Shoguns were no dummies, especially the first one, Togugawa Ieyasu. He knew what Roman influence had done to Europe. It was colonization by Roman controlled countries that the Shogunate feared, and not so much the pure non-political gospel of Christ, but any political connection with the gospel that made the Pope the supreme authority as most Roman Catholics consider him to be. This is not just my opinion but was confirmed by a learned Japanese friend.
For more information about the Jesuits, please see Army in Black