That new religion, completely distinct from the Japanese concept of spirituality, introduced more concrete systems of metaphysics and worship to the island. Buddhism rapidly gained popularity and now makes up the largest group of people in Japan with a declared, affiliated religion, and by a wide margin.
Christianity arrived in a meaningful way in 1549, with the landing of St. Francis Xavier, more than a thousand years after Buddhism. Xavier found great success in converting the local population, with tens of thousands of converts made by the Jesuits under his leadership.
To this day, children as young as elementary-schoolers learn about the life and mission work of Xavier in schools, where he is depicted in the traditional icon: clutching his burning heart and staring lovingly up a crucifix that extends into heaven.
Xavier's life and success converting the Japanese en masse to Christianity before the mass executions of the Edo Period are far better known in Japan than in the West.
But despite this familiarity with the man, there's virtually no familiarity with his faith.
"Since Christianity came to Japan from Europe, and thereupon assumed the role of introducing European culture to Japan, it left an image of Christianity as a foreign religion," Kikuchi told CNA.
An interesting situation can be extrapolated by comparing the numbers of self-reported Shinto practitioners versus self-purported Christians in Japan.
Christians make up 1-2% of the population of Japan. Less than half are Catholics.
While more than 90% of the population reports participating in Shinto rituals and festivals, less than 5% report any official ties to a sect or rite of Shintoism. They are participating, but they do not say they believers, and don't consider themselves followers.
"At present, Shintoism is still at the framework of traditional events (festivals) of local communities in Japanese society, and the presence of shrines and temples is widely accepted as something ordinary," said Archbishop Kikuchi.
"On the other hand, the church is still trying to find its specific role in the local community, perceived as a special place."
All this considered, Archbishop Kikuchi finds the idea of Japanese identity being compromised by conversion to Christianity to be unfounded.
(Story continues below)
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"In the first place, Japanese society is quite indifferent to religion. It does not matter whether you have one or not," said the archbishop.
"Therefore, becoming a Christian or belonging to any religion for that matter does not make one any less Japanese."