But then it’s stated oddly. It’s more like bears are encroaching on human territory rather than people expanding into bear territory.

Eh, I don't think there is much active encroachment happening any longer. Japan is no longer growing into its rural areas so much as receding from them.

Also, under certain constructions of the word "territory," (including the legal one) all territory in Japan is human territory. The bears are allowed to live on some of it but it is at the sufferance of the Japanese people.

See also headlines that refer to “shark infested waters” instead of “human infested waters”.