Young Arcus
Here is Arcus at the age of 8 during the festival when he was awarded for having the smallest waist among the imps of his age.
This ancient practice was invented by Sun-worshippers who used waist cinching to make their lower bellies ideally round to resemble the Sun.
For this week of festivities his priests dressed him up in a bright yellow dress and rounded up his belly with a tighter belt than usual to make it resemble the Sun. Arcus wasn't enjoying it as much as everyone else, not because of the belt's size but because of so many people coming to stare at him and discuss his impossibly small waist XD
Nobody else in the kingdom at the moment had a waist smaller than the Prince's. Even cultists who used waist-binding for the purposes of sorcery weren't as good as the boy.
Notably, his training technique wasn't painful at all, after all nobody would dare to hurt a Prince. It was a magical work of balms made of rare ingredients, a well chosen diet and a very specific massage performed by the best masters in the kingdom which helped to rearrange the internal organs properly without affecting the work of the digestion system and blood flow... but I can't give out any more secrets of his miraculously soft waist, as I fear these demons might come for my soul, haha XD
As for Arcus himself, it wasn't his choice and he often envied other kids as they moved and played freely while he had to be very careful and delicate with his wasped waist, moving, sitting and laying only as instructed... He was specially jealous of young acrobats and dancers who sometimes performed at festivals such as this one to entertain the crowd with their fantastic tricks and wondrous flexible postures, while himself he had to stay calm all day. But the priests kept assuring him that endurance and patience are good qualities for a Prince...
In his late teens, however, his life got a twist that pushed him exactly in the direction of those whom he envied so much. One day he was enslaved by King Asmodeus who forbid him to wear the belt and forced him to become a dancer and contortionist. Arcus had some of the most enjoyable time of his life, though later he talked the King to let him wear the belt again.