One is a agrarian and the other urban.
Two types of completely different civilizations clashing.
(I often wonder how dense you could get and still be ecologically harmonious using e.g. Permaculture; you might be able to reach the density of a town.)
> There's a huge confrontation.
Which I agree with, history shows that urban folks and rural folks are often at odds, to put it mildly.
However, you also said,
> Two types of completely different civilizations clashing.
Which I disagree with, rural (not wild) areas are just as artificial and man-made (for all that they have more foliage and critters per area) as cities. Agriculture and urbanity have proceeded hand-in-glove. Farms and cities are both parts of the same civilization.
What you're describing is hunter-gatherer (which IS a different civilization, in my opinion, from urban/agriculture) even if it's happening on the fringes of some other civilization.
As far as i know, and I'm not a historian, there haven't been farming (rural or pastoral) civilizations without some town or city involved, farms have always been the umbra of the city.
There were nomadic herders, hunter-gatherers, and farmer/city-states, but there never were cities without farmers nor farmers without cities, ever. So I say they are part of the same civilization even though they are in tension within that system.
Nomadism and foraging is the opposite of urbanization and agriculture.