I have done some research about BDSM relationships that are considered to be patterned off of BDSM values and principles, which are quite clear. It is a kink that is very much based on mutual trust and understanding - a lot of people just think of it as Dom/Sub or physical "abuse" or "torture." But in really, it is something that only works if you start from a position of trust.
It began with real conversation about limits and absolutely off limit things. Ethan shared the Doms, then we talked about mine. Ethan then made commitments he promised to uphold under any circumstance. Trusting that was the jumping off point. I either had to trust he would do as he said, or I was fucked regardless - either because I'd feel my limits and the consent I gave was not honored or because he was up to something nefarious. Neither ended up being true.
Very quickly, I saw no examples of him not honoring our agreement and his commitments and many relationships, the trust was then easy to invest fully in. Psychologically, it calmed any tension and anxiety I had, made me more open to escalating physical/mental experiences that would come... I'm thankful it was never abused, but I would have done nearly anything by about day 3 had they asked me.