Even as Jin interpreted the way he wished to, a quick clarification (which Kiyu eventually said it was no fun for Jin) from the System enabled Jin to find out that Rex was the biggest 'big brother' of the foxes aside from Kraft.
Kiyu was not wrong.
Rex did purchase the cities that connected to the Pandapolis that enabled the Seven Cities to relocate to those locations. But that was after blockading each and every city with the aid of the Demon Armies. Those armies were left on the outskirts of the cities for days and some were even months.
Nothing could go in but people can go out… Just that those people cannot go back in again. This inaction from the Demon Armies made the cities, the travellers and merchants afraid. Even though they were not breaking any laws by staying on the very outskirts of those cities, there was no way for the city to survive without resources from other towns and merchant groups.