Almost 200 17th-century Japanese Christian martyrs are headed for canonization in the Catholic church. The martyrs were killed when the Japanese shogunate banned Christianity and began persecuting believers in the early 1600s.
The success, persecution, and persistence of Christianity in Japan is quite a dramatic piece of history, but not one that gets a lot of attention. Interestingly, while the practice of Christianity was almost completely erased from Japanese public life after the 17th-century persecutions, a small movement of underground Christians continued to practice their faith in secret, passing the faith on in hiding for hundreds of years before the restrictions on Christianity were eventually lifted. There's an excellent article by Patricia Downes that tells the story of these "Kakure Kirishtan" (hidden Christians).
Particularly noteworthy is the way that their theology and beliefs, isolated from contact with the broader Christian church and without ready access to Scripture or traditional church ceremonies, slowly evolved until they no longer bear much resemblance to orthodox Christianity. From Downes' article:
Following Buddhist tradition, their priesthood is hereditary, passed down from father to son. A celibate priesthood would be too conspicuous in Japanese culture. Prayers were therefore passed down in the isolation of families and villages, resulting in little or no standardization. This was a religion truly hidden — devoid of documentation, a public hierarchy, and external structures....
According to Whelan, the priests do not understand what they are reciting, and neither do they seem very interested in their meaning. "It is not very relevant to them," she said. Their significance is more spiritual that historical or theological, she said.
With their Scripture forgotten, no real creed, and no catalogue of doctrines, the practice of this religion has evolved into a narrow fidelity to ancestral rituals.