Annexing = Taking. Just because they take it once, doesn't mean Kusari, when they come to take it back, the aggressors.
From a gameplay perspective this group would do very little other then sitting in their new home system hoping the KNF or a stupid trader rolls by that they can interact with. Because if they leave they're either pirates or foreign nationals invading Kusari. Both of which get them treated to the same thing as GC/BD.