Audacia responded in a soft voice:
"This is based on the fact that, apart from the essential working population, several nearby secondary planes are utterly devoid of inhabitants."
"I once had the fortune of visiting the agriculturally developed Harvest Town, which originally was a populous secondary plane. Now, apart from a group of professional farmers who have obtained licenses from the Truth Sect, the only remaining population consists of the knight regiment that resides in the town."
"They've driven people to the material plane, leaving the empty secondary planes behind. Different secondary planes are used for extracting different resources, including human resources, which have become one of the exploited."
"After losing their land, a large number of residents from the secondary planes were forced to enter the cities, where they can only work for the affluent classes to get by. They are nominally free, but in reality, they aren't much different from slaves."