Side Vocation by Sickmind (Archive Link)
This is another one of my favourite stories ever. It would have probably been better if the author had split it into two parts, but that doesn’t really matter. It’s about this guy who trains girls sent from Asian countries for some specific purpose that isn’t obvious. This starts with corsets and very rapidly escalates to very extreme fetish outfits, torture and slave training. Things like breast implants and other body modifications are also elements. The part I most enjoyed were the ones, where the trained character is in public hiding some kind of fetish outfit.
I can only recommend reading this story to learn some more about the extreme version of hidden fetish clothing and I insist that you have to read it to the end, as the outfit described in the last few paragraphs have given me ideas ever since I’ve first read this work a few years ago.