I’ve written about this else where on the forum, however it fits here as well.
The following is what transpired one afternoon, while my sister an I were giving each other a couple of enemas. While she was doing me, she accidentally masturbated me in a way neither of us understood at the time, until it happened. As teenagers we were in the habit of giving each other enemas after school from time to time. A year or so into this activity, while she was giving me an enema in the knee chest position using a douche nozzle, it started too slip out. When I told her about the nozzle slipping, she reached down and pushed it back in place with a little twist. It really took me by surprise, it felt so good, and I let out a moan. Unbeknownst to me, my moan aroused her curiosity about what had just happened. She told me later, my moan made her want to see what would happen, if she moved the nozzle back and forth without stopping. As the bag emptied and I was holding a two quart soapy enema, she did just that. Again, I started moaning as she moved the douche nozzle back and forth, and she didn’t stop this time till I came all over the towels beneath me on the bathroom floor. Taking both of us quite by surprise. Neither of us realizing, I could ejaculate without touching or moving my hand back and forth on my hard penis. We’d watched each other masturbate at night after going to bed an I had only recently been coming when I had an orgasm. Nothing like that had ever happened before that afternoon. I was holding a two quart enema as my sister moved the douche nozzle back and forth in my anus till I came all over the bathroom floor. When it was over an I was on the toilet expelling, I asked her, “what possessed you to do that?” She replied, “when you moaned as I put the nozzle back in place. I got curious and wanted to see what would happen if I moved the nozzle back and forth without stopping. I never realized you would come like that.” My only reply was, “I didn’t either.“ When I finished on the toilet, I got back down in the knee chest position for my rinse enema an I told her, “do it again.”
She did as I asked, only this time she starting before the enema bag was empty and continued while I held the two quart enema, till I came again. While I was on the toilet expelling my rinse enema, she fixed a two quart soapy enema for herself and hung it up. When I finished and stood up, she got down in the knee chest position and told me, “do me, I want to see what it feels like.” I did her just like she’d done me during my rinse enema, starting before the bag was empty, for both her soapy and rinse enemas. Like me, she moaned the whole time I was doing her during both enemas, till she had an orgasm. While I was cleaning things up, and she was on the toilet expelling after her rinse enema, I asked her, “I take it from your actions, you really liked it?” She replied, “we’re doing this again, I’ve never felt anything like it, it was great.” After that afternoon, it became a routine thing between my brother, sister, an I whenever we gave each other enemas.