I've never been a fan of pain for any reason, and it's an instant anti-aphrodisiac for me. Now some sensations that might be described by some as mild pain like a very light spanking or a crampy enema are tolerable. Now the fantasy or real life experience of being restrained or bound so that another person can subject you to various sexual and related stimuli as in the OP's question I think are quite common. Being bound but knowing you'll experience perhaps unknown but likely exciting or sexual stimuli while having confidence that you are nonetheless safe is very appealing to many, including myself. For example, I love taking enemas, especially wearing rubber suits and hoods, and I enjoy doing it by myself without question. However I quickly learned in my 20's that if an interested, cooperative and trustworthy partner did it to me after restraining me, the loss of control and thus submission to their whims was even more exciting than the original enemas.
So safe restraint or bondage by a partner is often a strong aphrodisiac. The exact nature of what you might either fantasize or do in restraint in real life just depends on what you find sexually arousing and satisfying. Though it's incomprehensible to me personally, many on Zity are truly excited or aroused by pain, so they might frequently fantasize about pain while bound. For me, it's several kinks, but frequently including large, long embarrassing humiliating enemas dressed in a lot of rubber given to me by my fantasy Domme. Now I do enjoy those enemas being very large, 4-5 quarts, with the Domme forcing me to hold them for a long time as I deeply enjoy the bulk and weight and distention from the enemas, but no obvious or frank pain except perhaps a bit of mild/moderate cramping. To me, a lot of internal enema pressure producing outward distention are to me merely strong sensations, not pain. Bring it on!
I'll leave all the super-crampy frankly painful enemas, no matter what the size and retention time, to my more adventurous Zity friends. We all enjoy what we want. Play strong but safe.............
Eric