As I sat down to work I decided to go through my favorites and pick out a few new toys for my sister to enjoy. I settled on a buttplug and a remotely controlled vibrator, and as I was hitting the order button I heard the sybian click on from the other room. I smiled and resigned myself to sit this one out as I got focused on my work.
I managed to speed through my tasks in a few hours despite my persistent hard on, and I got up to check on my sister. I hadn't heard the sybian shut off the whole time, and when I entered the living room it was clear she had been riding it the whole time. She had a chair propped in front of her to lean on, and her naked body shined with sweat. Despite already getting intimately acquainted with her, seeing her writhing there in the middle of the room gave me pause. I watched her in silence as I again thanked whatever god had granted me this amazing gift.
I noticed that she had repositioned the dildo further forward on the sybian, and it was now in her pussy all the way to the hilt as she ground against the base. Her whole upper body was leaning on the chair in front of her, and her eyes were bolted shut with her face seemingly permanently contorted in pleasure. She didn't hear my footsteps as I approached, apparently she was too in her own world of multiple orgasms to pay attention. I quietly stripped behind her, grabbing the bottle of vegetable oil as I knelt down. I made a mess as I poured a liberal amount on my cock, thankful that I had hardwood floors in this room.
She still hadn't seemed to notice me, so I skipped pouring any on her as I readied myself to mount the sybian behind her. Her ass was spread open obscenely in front of me, and it took a bit of self control not to dive in and eat her ass out. My cock ultimately won the battle, and I lined myself up with her quivering asshole as she moaned obliviously in front of me. I squirted some oil on her hole as I pressed the tip forward, easily slipping myself in.
"WHA-OOOOoooohhhh..." she yipped as she became aware of my presence behind and inside her. I wish I could say that I slid all the way in to the base on the first thrust, but she was far too tight for that despite the oil.
I said nothing as I worked my cock deeper and deeper, inching closer to my goal. She kept her body weight resting forward on the chair, and I leaned in to press myself against her. The vibration of the sybian was strange on my balls, but it was an afterthought considering how her tight ass was squeezing my cock. As I got close to bottoming out, she started to squeeze harder, pushing me as I pulled out and relaxing when I pushed back in. We communicated wordlessly as I fucked her, and before long I had made it all the way to the hilt. We both moaned a little as I reached my destination, and I took a moment to do short, hard thrusts with her ass pressed against me.
She immediately reached behind us and put a hand on the back of my neck, holding my body to hers. I reached around and took each of her breasts in my hands, firmly but gently kneading them. I had wanted to pull back and start railing her, but she seemed to like our current position and the sybian complicated things a bit.
The way her ass gripped my cock made me feel like we were two puzzle pieces, and the vibration of the sybian started to feel good on my balls as her sweat and the oil ran down between us. I moved in and out of her soft and slow, leaving all but the last inch of my dick buried inside. She threw her head back as the pleasure grew too much for her, and she came around both cocks stuffing her holes.
Her ass got several degrees tighter as she trembled in front of me. I leaned in and lightly bit her neck as she forced me partially out of her asshole, but I wasn't about to stop. Her legs were shaking and each of her holes was constricting and releasing as she started to come down from her cloud. I didn't let her come all the way down before my lust took over, and I started to really let her have it.
I reached forward and knocked the chair away from her, and pushed her body forward until she was on her hands and knees. The dildo angled obscenely, but it kept its suction and filled her more deeply as I scooted her back onto my cock. I raised up off the sybian and got leverage on her by placing one hand on her back and squeezing her hip with the other.
She moaned like a whore as I bottomed out over and over, racing to get myself off in her ass. Her sweaty hair fell into her open mouth as she gasped, and the sexy image brought me closer. I had no idea how many times she had gotten off today, but the sweat kept running down her ass and helped keep my cock lubed up as I plowed her.
"FUCK," I yelled as I watched her ass cheeks bounce.
"Don't stop, don't stop, don't stop, keep fucking me, keep fucking me, fuck my ass," she chanted with her face pressed to the floor.
"I'm gonna fucking-," I started to say before she cut me off.
"Keep fucking, keep fucking, keep fucking," she insisted as she started to fuck back onto my cock, not caring about my impending orgasm.
"Holy SHIT," I breathed out as I started to unload in her ass, letting her take control of the tempo. I gripped her ass hard as I shot rope after rope of cum in her ass, but she showed no signs of slowing down at all.
Her legs were trembling again as she approached another orgasm, and she started to talk to me again.
"I'm a whore, big brother. I'm a fucking whore. Please don't stop, please use my ass again. Please, please, PLEASE," she started to beg. Her filthy mouth kept me hard with no issue, and I positioned myself to give her what she wanted. I reached forward and pulled her arms behind her back, pinning her down in an obscene position and removing her leverage.
"Oh yeah? You're a fucking whore? Who's whore are you? Who do you belong to?" I asked through gritted teeth as I leaned over her.
"YOURS, I'M YOUR FUCKING SLUT. USE ME, USE ME TO CUM AGAIN, CUM IN MY ASS, PLEASE," she spat back to me, and I tried my best to not disappoint.
I leaned into her and her tits pressed into the floor, the sweat pooling around her. I started to fuck her slow, but hard, and she gasped each time I slammed down into her. The sybian still hummed underneath us, but I barely noticed it at that point. Her asshole barely loosened as I plowed her, and she kept up the rhythm of squeezing down each time I pulled out. I felt the mixture of sweat, oil, and cum around the head of my dick, and soon enough I was getting close to nutting again.
"You have the tightest ass I've ever fucked," I growled to her, "I'm already close to cumming again."
"Please...," she whined softly, "please use me, I need my brother's cum."
She knew just how to push my buttons, and in response I pushed all the way in as I readied myself.
"You want my cum? You're gonna have to earn it. Milk my fucking cock with your ass, you slut," I demanded. She responded by squeezing her tight ass on my cock over and over as I leaned in and forced my cock to stay buried to the hilt. She tried her best to force me out, but gravity kept me inside.
The sensation was incredible, and soon enough I was ready to shoot again.
"Fucking WHORE," I exclaimed as I reached forward and pulled her hair the way she liked it. She yipped as she felt me unload in her ass a second time, both of us savoring the feeling. I lost control and fell forward onto her, sliding her forward and off the sybian. Somehow I managed to stay lodged inside her, and she didn't let up trying to milk my cock.
"More... give me more," she moaned out as she squirmed underneath me.
"You're a greedy slut," I told her with a laugh as I rested on top of her, but she wouldn't let it die.
"Don't you think your sister is sexy? Don't you want to use me again?" she cooed to me softly. I didn't think it was possible for me to go three times in a row, but I said nothing about it to her.
"Do you want a load in your tight cunt?" I asked, hoping to use the time spent repositioning to try and build up the stamina to go again.
"NO," she insisted, "don't pull out, I want you to fuck my ass until I cum again."
My muscles were sore and screaming at me, but I steeled myself. I was determined to make the most of this once in a lifetime experience.
She reached forward and grabbed my hands with hers as I braced myself on the floor. I pulled back and started another slow assault on her ass, and she looked back at me. She had a look of pure joy and pleasure spread across her face, and she grunted sluttily as we made eye contact.
We maintained our gaze as I started to speed up, punishing her tight ass. I knew my body was going to hate me later, but the way she squeezed my cock easily dispelled those thoughts. We spent several minutes like that, holding eye contact as I fucked her, and I felt our already strong connection deepening.
I noticed her eyes start to fog over and her mouth hung open as she took my pounding, and I again felt her thick thighs start to tremble. I picked up the pace with what little energy I had left, and she responded with another moan.
She started grunting as she came, and I did my best to fuck her as hard as I could. Soon she started talking, but I couldn't understand what she was saying with her face smashed to the floor. It became more clear as she started to wind down.
"I love you, I love you, I love you," she was saying softly, and it warmed my heart. I didn't fully know what our relationship was at this point, but seeing her transform from a whore into this pile of mush was both endearing and a turn on.
I eased up a little as I fell forward onto her, but my own orgasm was also inevitable at this point. She kissed my cheek as my head fell beside her, still slowly fucking her. She started to milk my cock again as she reached up and gripped my hair. I got closer and closer to the edge, but I was running out of energy.
"I love you, cum in me," she said lovingly, "cum for your sister." That was all it took, and my mind exploded as I bottomed out and unloaded. She kept up her milking, and moaned softly and sexily as my cum started to leak out of her ass around my cock.
----
Despite her hormones, we took it easy for the rest of the day after that. The next day I caught her sunbathing outside on the back deck, topless despite the crowd within eyesight down the beach. I thought about scolding her, but the sight of her heavy tits out in the open also turned me on. I looked again and figured that the crowd was far away enough, and took a seat next to her.
"Hey bro," she said groggily as I woke her from her nap.
"Hey sexy," I replied, "I see you've got the girls out, are you trying to show off?"
She reached up and jiggled them for me as she giggled, not saying anything in response.
