Erick Mead wrote:
Later Japanese systemization of the Kojiki Shinto attempted to "purge" it of "foreign" elements and interpretations under the Kokugaku (National Studies) in the nineteenth century. Hirata Atsutane, and Motoori Norinaga, were leading figures in this process and have been recurrently criticized for supposed "Christian" influences (as were others for being too "buddhist".)
I don't know enough real Japanese history to understand exactly what happened and when, but it's pretty obvious that the massive and rather public intermingling and availability of Chinese studies (particularly martial and related) has somehow been obscured at some recent time in history. Whether it was the 19th Century or in the 20th Century, it's hard to tell.
However, there are historians out there that seem to know that there was an open focus on Chinese body-technology and martial arts at earlier times... facts that seem to be almost fanatically denied nowadays in many corners. Western histories often parrot these nationalistic ideas and all it does is slow the search for information and sources, IMO.