Every single one of the Hunters of the B-Rank Hunter Party except for Stella had plenty of experience with these slave collars. Before the newbie Stella arrived, they often ventured into Gates known to have 'unique' monster life and then enslaved them, played with them, or just straight up sold them off.
Humanoid monsters like Elves, semi-intelligent demihumans, and similar such beings were their targets. Some of the Party members had weird fetishes, while others simply participated in this vile act for money. Whatever the case, all of them contributed one way or another, with some, like Dominic, John, and Lexi, contributing the most. They even started competitions to see who could enslave more humanoid monsters—the more innocent they were, the better.
