AHC: Syncretic Shinto-Christian Religion

Your challenge is to create a religion that is a combination of Christianity and Shintoism. This is a very interesting scenario since it does not involve just spreading Christianity into Japan but syncretizing it with polytheistic, indigenous Japanese religion. Now you might think "but polytheism is not compatible with Christianity so how could it be combined?". Well there is a precedent or model for the combination of polytheistic gods or spirits and Christianity: Haitian Vodou and Santeria. The basic model for how those religions worked would be that there is some higher, monotheistic entity that is impersonal and not directly accessible but is accessible through his intermediaries, each of which have control over different spheres of nature or reality, and which are worshipped or interacted with instead. This was the way in which African, primarily Yoruban slaves, squared Christianity with their indigenous religion.The cult of Santa Muerte also counts as an example. This sort of model could suit a syncretic Shinto-Christian religion very well with Shinto kami being repurposed as intermediaries like Yoruban gods were.

One way for this to be achieved would be a more successful Shimabara Rebellion which, while likely not going to lead to Christianity being widespread, would at least give it some renown or support as the "peasants' religion" like Buddhism became (to my knowledge) in Japan. Had it become more successful, and had greater support by the local nobility (there were already ronin who had allied themselves with the Christian peasants), you might have had more lords decide to become Christian and thus greater tolerance among the Japanese aristocracy. Similarly, the Shimabara rebels were Catholic and both the base religions of Vodou and Santeria was Catholicism (it appears Catholicism is well-suited for syncretism, who knew).

But you all are more knowledgeable than me. How will you all address the challenge? Bonus points if this religion obtains its own Catholic Church but oriented around this syncretic religion.
 
While not exactly Catholic, I can see Chinese monks that are Nestorian going to Japan to spread the Nestorian form of Christianity, and Nestorianism becomes the base for a Japanese Christian offshoot religion that combines Shintoism, Christianity, and maybe Buddhism, somehow.
 
This kind of sounds like what happens in the Nobunaga's Ambition TL where there is a "Japanese Catholic Church" because the Japanese government doesn't like the Catholic Church's affiliation with the rival Spanish, but the government isn't as extreme as the OTL persecution of Christians so merely demands they separate from the Catholic Church. Which given the demographics of Christianity in Japan, is suitable to enough of them they make their own church which I am certain would have characteristics of Folk Christianity and maybe among some worshippers, this true syncreticism. Granted, I can't entirely recall what the TL author had in mind for that.
One way for this to be achieved would be a more successful Shimabara Rebellion which, while likely not going to lead to Christianity being widespread, would at least give it some renown or support as the "peasants' religion" like Buddhism became (to my knowledge) in Japan
Christianity in that era was perceived by the Japanese along the lines of radical Pure Land Buddhism, and indeed followers of those Pure Land schools were often bitter rivals with followers of Christianity.

It's probably not surprising since there is evidence that Pure Land Buddhism in general arose from Manichaeism, and Manichaeism itself was influenced by Christian Gnosticism.
While not exactly Catholic, I can see Chinese monks that are Nestorian going to Japan to spread the Nestorian form of Christianity, and Nestorianism becomes the base for a Japanese Christian offshoot religion that combines Shintoism, Christianity, and maybe Buddhism, somehow.
The thing with Nestorianism is that in many parts of East Asia it declined rapidly. Like there were once Nestorians in the Malay Peninsula (not surprising since they traded with India), but they left practically no trace beside records in church archives. A Nestorian community in early Japan (8th-9th century maybe) would be very much foreigners confined to Kyushu and make few converts. That era was the height of Japanese manorialism (shoen) where the Imperial court and allied Buddhist temples controlled the land, peasants, and economic activities occurring there. They could hardly have radical new movements appearing, and despite popular belief, all they'd need to do is expel Christians from their country and that would be it, just like it was in China.

The other potential is the second height of Nestorianism in China during the 13th/14th century under the Yuan dynasty, but that too is obviously foreign. In that case, they'd probably end up blending with Pure Land Buddhism (which was spreading among peasants in this period) and not being very Christian other than maybe having iconography in their temples that looks like Jesus. It would be too easy to identify Christianity as another product of the foreign invaders and expel it.
 
I’m assuming “Pure Land Buddhism” was something the average Japanese person was highly suspicious of and generally against — Is this correct?
There were many different Pure Land sects, some of which were mainstream among all levels of Japanese society, others like the Ikko-shu sect deemed dangerous to the social order because they were associated with lower classes.
 
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