Since Christianity was pretty thoroughly hunted down in the Edo period, I was wondering if Christian traditions in Japan at the time deviated in any ways from mainline Christianity?
Basically, when Christianity became legal again in the Meiji era, did foreign Christians think Japanese Christians were doing religious rites or rituals in a strange or maybe antiquated way? Maybe it was because they could not get information from the main Church, or maybe as a consequence of having tiny numbers/hiding for so long?
There is always more to say, but I wrote a reply to a similar question here a while ago, and you might like to review that response while waiting for fresh answers to your query. As you suspect, the number and the extent of the ... deviations ... that occurred over the centuries before Christianity re-emerged in the late C19th were pretty considerable, and pretty remarkable.