What if the Ainu of Hokkaido, via Japanese influence, were to develop in a more agricultural, urbanised and ultimately perhaps even quasi-unified (in a dark ages Ireland sort of way is perhaps the best we'll get) direction?
The Japanese would of course likely still come along and conquer them when they get the time- they'd probally do it earlier than OTL in fact with Hokkaido being a far better target- but with a pre-existing idea of nationhood and larger native population...it could all go rather Ireland.