Watching TV naked

I am sitting between Riley's bare legs and leaned against her bare torso with her boobs on my shoulders. I am also naked on the couch, watching TV with my equally naked sister. My cock slowly became fully erect again when the movie we're watching approached a sex scene.

Riley glanced at my erect 20 inch cock before looking back at the movie. She slowly and gently grabbed my balls and started fondling them. I started moaning softly. I cannot let her get away with it so I start playing with her boobs; my right hand on her right breast and my left hand on her left breast. She started moaning softly as well. Riley moved her other hand towards my balls, now both her hands are stimulating my balls.

I lean my head back with eyes closed, enjoying the pleasure. I am still playing with her boobs. My shaft is ignored but I feel it getting harder and bigger as well as felt the precum dripping. We were stimulating each other for 5 minutes until the sex scene ended. "Anna, your cock is bigger!" I open my eyes and look at my cock. The head of my cock is above my own head! "What?! How did it get this big?!," I get up in panic but trip and fall on the floor, the sudden weight increase catching me off guard. I fell face forward but I fell on my cock, making me grunt in pain as well as cause my cock to shoot a stream of precum on the floor.

Riley helped me up, but I am still unbalanced thanks to the new addition to my body, which is this darn cock. I managed to regain my balance but this cock of mine is unnerving, now that it has grown more than half my height. "How big is it now?," I asked worryingly. "I'll be back with the measuring tape.," Riley said before going to get it.

She came back with it and started to measure my cock. "Thirty inches, Anna. Impressive.," Riley complimented. "What did you do to make my cock grow? I don't remember cumming while watching the movie.," I asked her while folding my arms and a frown on my face, though it might be hard to take me seriously since I am naked with a huge erect cock. "I didn't do anything besides...scrotum stimulation. Does your cock grow when your balls are stimulated?," Riley spoke curiously, "I don't know!," I replied.

I then felt sis push me to the couch, making me sit there, "What are you-oohhh.," I tried questioning her motives but she started sucking and licking my balls. After a minute of ball sucking, she stopped. I hear her use the measuring tape. Looking at the length, my cock indeed grew, now 31 inches, more than half my height.

"Your cock does grow. Let us see how big you can get.," Riley said, "Riley, wai-oooh!," she started fingering my pussy and sucking on my balls at the same time, interrupting me. I feel the fingering get faster until I cum from my pussy.

Riley had continued this for 15 minutes. I ended up cumming a few times from the pussy. It looks like my cock stopped growing a couple minutes ago. "My god, 42 inches! That is almost four feet!," Riley said in awe. I stand up, a little wobbly from the orgasms. My cock is a few inches below Riley's height of six feet! And it is 3 inches thick! And my balls are the size of Riley's fist!

"Riley, look at this! How am I supposed to go to school tomorrow?! Or anywhere outside for that matter?! It was already difficult to manage a 20 inch cock, but a 42 inch cock?! Seriously?!," I yell in anger. "Relax, there is a solution.," Riley said, trying to calm me down, which was working, "What's the solution?," I asked grumpily, "You're a grower. You have a very small flaccid cock. In order to make your cock flaccid again, you need to cum.," Riley finished. I realized she made sense.

"Where do you suggest I cum? If my cock is this big, it probably releases a huge amount of cum.," I voice the concern, "In the shower. Once your done cumming, the water will wash it off.," Riley finished. She then grabbed my shaft and started licking my cock head. "Now, follow me. Let's take care of that erection.," Riley said, leading us to our shower, with her tugging at my cock as we go there.