If you don't get a response hear, you could consider x-posting to /r/AskAnthropology.

As /u/Ozfeed mentioned, Bushido as a concept did not exist in premodern Japan. It was largely a creation of the 18th-19th centuries. Chivalry as a cultural concept is dicey, even in European history, where it originates. Chivalry in Japanese culture... I wouldn't use that word. Medieval Japanese people aristocrats certainly had ideal behaviors - performing and writing poetry, for one example, later tea ceremonies (among warrior elites). If you're thinking of chivalry more as an honor-on-the-battlefield thing, Japanese warfare has a time honored tradition of switching sides mid-battle, which in our time we would definitely consider to be the opposite of honorable, but here we have to meet them on their terms. This was expected battlefield behavior. These types of behaviors aren't related to religious practice though. The only religious practices related to warfare that I can think of (I'm sure there are more, but off the top of my head) would be things like patronizing temples and shrines, carrying talismans, or inscribing deities names or symbols into blades. See Conlan State of War, he has a whole chapter on warriors and religious practice.

I'm not sure what you mean by "native tribes" though. On the main islands (excluding Hokkaido), Japanese society hasn't been considered "tribal" for around 2,000 years. Between then and even the beginnings of recorded history on the islands, religion, language, society basically as a whole changed pretty radically. Did the warriors in this period have ideals that carried over a thousand years into when we have documents written by warriors? The archaeologist in me is saying "We can't prove one way or another" because nothing is recorded and the conditions for the cultures are so different, and the historian in me is saying "highly unlikely". Courtly culture developed during the 8-11th centuries in the cultural crucible that was the Heian capital (about 600 years after anything that might be considered even remotely "tribal"). Warrior culture picked that up as an ideal and developed its own additional ideals during the centuries of intensified warfare between the 14th-16th centuries. Then 18th-19th century nostalgia picked all of that up and did their own thing with it, and those are the ideals current popular thinking about Japanese culture and religion reflects.

On the other hand, if you're thinking more about the Emishi/Ainu connection to medieval court or warrior culture (with warnings about the disconnect between ideals of then vs. what we think of as "bushido" now, same as above), then big yes. Hiraizumi is a fantastically interesting example of the cultural borrowing and adaptation that the Northern Fujiwara (Emishi) did in establishing hegemony in northern Honshu during the 11th-12th centuries. This book does a really good job of discussing the details of that period, both from a cultural (courtly/aristocratic, political, and early warrior) and religious (Buddhist and Emishi tradition) perspective.

I hope that helped. Please feel free to ask if you have any more questions.