An interesting setting...

There's got to be a plot in there, a conflict other than "'yes you will', 'no please don't'...

Suggested plots. Ignore the female pronoun if you prefer a male (or shemale) character.

A 'Taming of the Shrew'-like competition to make the most dramatically altered sub.

A young victim has to outthink, outsmart, and outlast' her fellow prisoners to survive the society's yearly housecleaning party. Twenty to thirty slaves, and only one gets to see the new year. Subs compete to be the favorite of the Society, screwing each other over for a shot at survival

An FBI agent tries to infiltrate the society and learn its secrets, only to be taken prisoner. She attempts to escape using her training and her wits. The Society holds a torture competition to see who she'll call master.

Maybe a view from a holding cell as prisoners reflect on their treatment and consider escape...