Ben and Susan’s unusual relation – part 4

I heard a sound from behind me and turned my head just enough to glance at Sherin who I had almost forgotten was there. The front of her pants was open and her hand was buried under her panties, masturbating freely at the show Susan and I were giving her. I’d expected it to happen as she got more comfortable around us, although she was a bit quicker about it than I would have predicted. She met my gaze for a second as I looked at her and seemed embarrassed, but didn’t stop what she was doing.

Susan continued fucking herself on me as I turned back to her, although she faltered slightly as I grabbed the base of her butt plug. As I had done back in the clothing store I merely played with it at first, wiggling it around just to see what kind of reaction I got. My sister had a different idea of what I should be doing.

“You’re gonna do it aren’t you?” she said. “You’re gonna fuck me back there.”

“Do you want me to?”

“Duh, that was the whole point of getting ready for you. You think it was just for fun? Actually, it was kind of fun when I think about it.”

Susan giggled softly to herself as I decided on my course of action. It wasn’t really a difficult choice when it came down to it, it just seemed like our first time trying anal should have been somewhere a little more traditional. Like in a bedroom.

I pulled on the base of the butt plug, slowly fighting against the resistance Susan’s ass put up trying to keep it in. As the widest part made it past her outer ring she moaned and stiffened up while her pussy squeezed my cock hard. Once I had the butt plug out I waited for Susan to recover a little before trying anything else. Even after her pussy relaxed it was a couple minutes before she straightened back up to her initial stance.

“You still want me to do it?” I asked softly. “That seemed pretty intense.”

“It was kinda,” Susan said. “It’s just so… bad having my brother playing with my butt like that. I love it. Although I think if you’re not in my pussy at the same time it won’t be so much for me and I could handle it better.”

“Okay, but you have to tell me if it hurts or if you want me to stop for any reason alright?”

“Promise.”

Susan’s asshole was still lubricated from where she’d put in the butt plug and my cock was covered in her pussy juice. I thought about asking if she had more lube with her just in case, but decided to at least try it first and see how easily it went. It wouldn’t be completely new to her this time so it might be okay.

I placed the tip of my cock directly against my sister’s anal opening and pressed gently, but with gradually increasing force. She pushed back and slowly her asshole reopened for me and let me in. As soon as the head of my cock popped inside her ass she froze and I immediately stopped moving as well. A small growl of pleasure emerged from her and her back arched as far as it would go.

“Are you still okay?” I asked.

“Fuck yes, this is amazing. Don’t you dare stop.”

She started rocking back against me, not enough to really drive me any farther into her but just to encourage me to keep going. That was all it took for me since already the feeling of being in my sister’s ass was incredible and my instincts were urging me to start fucking her for real.

I couldn’t go as fast as I was used to with her pussy of course, her ass was tighter and despite what she was telling me I knew she still wouldn’t be ready for anything too rough back there. On the other hand I probably wouldn’t last that long even going slowly, not if it continued to feel as awesome as it did.

Alert for any sign of discomfort I thrust my hips forward, pushing a little deeper into Susan’s ass. Unlike regular sex I found my movements had to be more purposeful, more controlled, but it was worth the effort.

“Shit, gonna cum again,” Susan mumbled.

“What already?”

My cock was only a little over halfway inside her, maybe two-thirds at the most, and I hadn’t even started to properly fuck her yet. As she had warned me though she was soon cumming again, collapsing forward onto the desk as her orgasm drained the strength from her arms.

“You have no idea how good this feels,” she said eventually, having recovered enough to speak again.

“I think I’m okay with that,” I said.

“You better cum soon or I’m just gonna pass out.”

“Alright, but are you-“

“Just fuck me, I’ll be fine,” she interrupted.

I had my doubts, but I felt the very beginnings of my orgasm approaching and that made it hard to resist too much. Taking a deep breath I thrust into her harder than before, finally burying myself fully in her ass and getting only a soft groan from her. I again had the worry that maybe we hadn’t used quite enough lube to allow me to fuck her as easily as I should have been able to, but it was too late to do anything about that.

After a few strokes I found it getting smoother, especially with Susan helping out a little. She still didn’t seem fully over her orgasm and the constant anal stimulation almost certainly had something to do with that, but she still pushed back against me in time with my movements.

It wasn’t long before the warning signs became more urgent and it was all I could do to keep up a steady pace until the very end. I didn’t even consider pulling out, though I realized after that Susan wouldn’t necessarily want me cumming in her butt. She clearly didn’t mind though since she made a noise very similar to a contented purring as the last of my cum shot into her.

I stayed exactly where I was even after I finished, capable of movement but failing to see the appeal. It would have been nice just to fall on a mattress and curl up with Susan for a while, although that was purely wishful thinking under the circumstances.

It was only when I felt my cock softening that I finally pulled out and stepped back a couple paces, unable to fully look away from my sisters just-fucked ass. A small amount of my cum had trickled out already and I wondered if I should wipe it off. Before I could Susan stood up and her skirt fell back down to cover her butt.

Once again, since she had been out of my line of sight, Sherin’s activities hadn’t really been a focus of mine. However her pants were now pulled down around her knees and she had a flushed, satisfied look so I assumed watching Susan and I had been enough for her to get off at least once. Seeing her state of undress reminded me that I should probably take care of myself and get my cock back in my pants. We all had some straightening up to do and there was no point tempting fate by leaving it until later.

“Could you hand me my panties?” Susan asked.

They were still on the floor from before, not far from where Susan was standing but evidently not close enough. I picked them up and handed them over, then watched as she put them on by lifting her legs up rather than bending over any more than necessary.

“Gotta stop all that cum leaking out all over the place,” she said.

“Yeah, good thinking,” I agreed.

If I hadn’t just cum the idea of my cum leaking into her panties all afternoon would have been more than a little interesting. As it was I just filed the thought away for later.

“Well I don’t know about you guys, but that may well have been the hottest thing I’ve ever seen,” Sherin said, having pulled her pants back up.

“Mmm, it’s definitely a contender for me too,” Susan agreed. “Now I just wish it was the end of the day so we could leave. Don’t know how I’m gonna make it through next period, it’s gonna seem even more boring after this.”

“You always seem to find a way,” I said.

“I guess. So hey, me and Sherin were planning on going to her house after school ‘because her parents are gone until tomorrow or something. You want to come too?”

Even in my fully stated state that wasn’t a proposition I would pass up right away, not that it was a guarantee anything could happen while we were there. I glanced at Sherin who gave me a small nod and a shrug like it was fine with her but my decision.

“Sure, why not,” I said.

“Great.” Susan leaned in to kiss me, then whispered quietly enough Sherin couldn’t hear. “I love you, you know.”

She turned away and headed out to the hallway with Sherin so quickly I didn’t have a chance to respond. I knew Susan loved me, just as I loved her, but it still made me feel good when she said it.

I sighed to myself as I realized that I too was going to have to sit through the rest of the day, and that there was no way I was going to be able to focus enough to make it worthwhile. Still, there was that evening to look forward to and the possibilities it held. For all I knew having a chance to recover before then might not be such a bad thing.