so, one person can create a barrier around themselves, just a few meters in diameter.
two people can create a barrier together that spans a city.
three people can make a barrier that spans... i'm guessing about a hundred kilometers, maybe a bit more.
and four people would probably create a barrier the size of a kingdom.
meaning, the fact that there are four noble families responsible for the great barrier is because their founders are the four barrier masters needed for the barrier.
going by the villain figure from the other noble family from the earlier chapter, i'm guessing the great barrier will be disabled or destroyed in the future and lias family will create a new one. plus maybe that friend from the friendly great noble family or the black haired boy.
though i wonder if there will also be a five people barrier at some point. that would be the size of the continent then, meaning the threat of those phantoms or whatever they were called would be dealt with for a while.