For several years I had a female submissive who was as obedient and compliant as I could possibly ask for. I'd trained her very carefully, and she was genuinely committed to exploring and satisfying her life-long need for control and domination. She always maintained an attitude of proper submissiveness, and she offered - or, when told to, simply provided or accepted - any manner of service that my desire or curiosity wanted. Our relationship was very much that of a mutually respectful dominant and submissive. It was also intensely sexual, with her serving me without hesitation in any way I required of her. Anal sex was almost always a part of our time together and she'd prepare for our meetings by cleansing herself thoroughly with several enemas. Corporal discipline was also very much a part of our relationship, and she understood that in addition to any other necessary attitude and lifestyle correcting discipline she would be punished for any lack of cleanliness, inside or outside, at any time. No matter how often she submitted without resistance to being taken anally she was never able to do so without copious tears and sobs and moaned promises of any other kind of service I wanted if I'd just not take her ass - which of course only made me want her tight, warm, always freshly-cleansed ass even more. She once said that I didn't really understand how difficult anal sex was for her, so I thought to find out for myself. I'd never been penetrated anally, except for enema nozzles and the like and occasional prostate massages. Frankly I was curious. And I knew that I could always tell her to stop if I needed to, which was certainly not something that she could ever tell me. So, after a bit of looking online at the infinite number and variety of dildos available and suitable for use on a man, I had her purchase something called a Feeldoe. It was a two-headed dildo with one smaller head to be inserted up inside a woman's vagina, and the other, more substantial (and penis-realistic) head to be used to penetrate the woman's partner. I made certain that she ordered the dildo early enough to take delivery several days before we met, thinking that surely she'd try it while she was alone. I didn't ask, but I think that she did try it. When we met, she was at first hesitant as I watched her insert the smaller head inside her vagina and then made her look at herself in a mirror and see the larger head cock-like dildo protruding and curving upward from the front of her vagina. I told her to lube her "cock" and my ass thoroughly, lay with all of her weight on top of me while I was lying prone and facedown on the bed, and then slowly ease the Feeldoe into my ass. I told her that I wanted her to show me what it was like to be fucked. It was an awkward situation as she slathered my ass with lube and after several attempts finally managed to control the dildo enough to direct it between my ass cheeks. Even though I told her to go slow, once she got the dildo properly aligned she forcefully thrust it all the way into me in a single stroke and then immediately started to withdraw and thrust it in again, over and over. I yelled (screamed, actually) and was instantly in searing pain. I felt like she was trying to rip me open. But then just as quickly I realized that she was using me and my ass in the same way that I used her. She didn't really know how to do otherwise. She did slow down for a moment, but then she started again with the in and out motion. At one point I raised my upper body off the bed by pushing myself up on my hands, but she immediately slapped my hands away and pushed me back down on my belly. She very quickly seemed to be enjoying what she was doing. She'd realized that her thrusting enabled her to pleasure herself with the head of the dildo that was up inside her vagina. She went a bit wild. I wasn't just experiencing anal sex as the receiver for the first time - I was being seriously fucked by a woman who was at the same time sexually pleasuring herself. I knew that I could stop her at any time I wanted, but I didn't. That's hard to explain, but I didn't. The pain gradually subsided and I became aware of a strange, new, pleasurable sensation of having a "cock" buried in my ass, and I experienced my first real sense of sexually serving and submitting to a dominant partner. And that happened even though I'd just wanted to feel what it would be like to be fucked. Eventually she managed to bring herself to orgasm and then raised up on her knees, pulling the smaller head from her vagina and leaving that bigger head inside me. I told her to slowly and gently remove the dildo from my ass and to then assume a position on her hands and knees on the bed, with her chest on the bed and her ass up in the air. Laying there on my belly with my legs opened and a dildo buried in my ass, I assume that I was trying to regain my sense of control of the situation by instructing her as to what to do. I told her that she'd probably taken me to a place that I'd regret going to, and that she was to be properly punished for doing so. She looked confused, but knew better than to challenge me. I then spanked her bare ass with a large leather paddle. Hard. For at least half an hour. Slow, well-placed, hard, both-cheeks-at-the-same-time strokes, over and over and over. In spite of her sobbing, guttural apologies for the way she'd lost control, paddling her ass until it was beet red and throbbing still didn't enable me to completely recover from the ego-bruising experience of having been so aggressively fucked by my own sub - or my own seeming willingness to accept and submit to the experience. Again, that's hard to explain.