The life in an island is a little unique in Japan, especially for smaller islands. There are hundreds of residential islands in Japan, where their relationship is quite tight as separated from others by sea.
The mountain area is similar in terms of a close relationship of the community, though it is much closer in the island, where it is more likely they share the same moral code. As Japanese, their way of thinking is totally Japanese, hence it does not feel weird, but unconceivable to foreigners.
In this code, it is prohibited to frame others in a trap. This is basically out of Japanese code, but it cannot be confronted when someone breaches this code in the urban area.
This type of the antisocial behavior exists proportionally in any places of Japan, which is the same in the island, but their irregular conduct is spread all over the place relatively soon. It depends on the size of the island, and the smaller it becomes, the more unacceptable the antisocial behavior is, which is directly denounced.
This environment is basically the same in the mountain area, but it is easier for outsiders getting into the area, as it is connected just by the road. Moreover, the community is quite small out there, comparing to the whole island which is at least consisted by several communities.
It indicates that the intelligence operation is not easy in the Japanese remote island, as it is nearly impossible to avail local people as the spy wants. The spy mission is basically out of the Japanese moral code and the police authority is not so strong as they are basically outsiders of the islands. They can live a life without a worry of the spy retaliation as far as living there.
As a result, the cooperation depends on a decision of the whole island rather than each individual who should think whether to cooperate with them or not, considering a favor for the whole island. Therefore, it is necessary for the police and spy to frame a subject as a dangerous person at first before availing local people against any operations, which is not an easy mission for the CIA and Japanese police intelligence.