The Ainu are the indigenous people of Hokkaido, the Kuril Islands, southern Sakhalin and the far south of Kamchatka.
While the Ainu are usually characterised as hunter-gatherers, they actually had some basic agriculture. Their crops package included crops like millet and buckwheat. Though agriculture always remained secondary to hunting, gathering, and fishing.
Is there any way for an Ainu civilisation to form, with urban areas, a more centralised government, and more advanced agricultural system?
Are there any crops that could be introduced to the Ainu lands to allow for this? IIRC, rice could only grow in the Oshima peninsula, the southernmost extension of Hokkaido.