The spy can be revealed when conducting an operation in the small island. The Yonaguni is not small in a size, but not populated especially in November, as the tourist season is already ended until then. There were tens of travelers at that time, the majority of those consisted of intelligence agents and their assets.
Generally speaking, they can be well branded into other people, as they are basically human being as well. As far as you have not understood what the spy is about, it is hard to notice.
I did not realize their identity at that time but recognized their behavior and background were weird. I just did not assume I was severely watched as I was not a criminal nor potential terrorist. There were many government officials and politicians who had known me, hence I had never imagined that I was filed as a dangerous figure.
As a reality, there were many spies around me in Yonaguni. They had disguised their true identity well, but it was hard to conceal, as there were not enough people to be mixed into. Eventually, almost all the individuals I contacted with were either local or spy.
This realization holds true to any other spies I saw in my life that I had not realized their true identity for a long time, but there were many traces that they worked to monitor me. There were always irregularities which became a lead to uncovering their intention coming near to me.
The last ten stories were just about whom I encountered in Yonaguni, but many residents knew who I am and who the spies are. They had definitely got a false alarm of me in advance, which was the reason why some of them cooperated with an operation of the police intelligence. This kind of operation is basically shared by the whole population in the island, which was the case for this mission.
They can run a covert operation more easily in the big city, but they can only disguise their identity as a traveler in the island, hence they cannot have hidden their existence as there were not many tourists at that time.
There were many traces of the spy operation, which was also true to the operation from the end of 2012 in Naseni islands. As a result, the local residents had known there was an illegal police operation, hard to hide anymore.