I couldn't stop thinking about what had happened. For days I jacked off to the memory of it but what I wanted most was to do it again. Emma had been very cool towards me, not talking to me for a day and only when she had to after that.

Finally, after 4 days, mom went out to the shops and left us alone for a couple of hours. Em was pretty much back to normal by then and I figured this was as good a time as any so I went looking for my sister. She was in the kitchen fixing herself a glass of milk. "Hi Em." I said lightly. "Can I see your pussy again?" Her mouth dropped open in shock. There was a rim of milk around her top lip. "I'll even diddle it for you if you want." I added hopefully.

"NO!" She yelled.

"Aw, Em..." I started persuading her.

"I said NO! Leave me alone." She turned her back on me.

"Please, Em. I'll let you see my cock if you want." She turned around with a look of surprise on her face. Fearing another rejection I added a further bonus. "I'll even let you watch me jack off."

"NO WAY YOU FILTHY PIG!" She yelled. 'Pig' was her favourite insult. She turned away and stalked past me carrying her glass of milk carefully with both hands.

I went to my bedroom feeling crestfallen. I pulled one of my porn magazines from it's hiding place but the familiar pictures just weren't exciting any more and I threw it aside. I was trying to think of a way to force my little sister to let me play with her pussy when there was a timid knock at the door. "What!" I called a little too grumpily.

"Okay Ross." Emma said as she came into the room.

"I'm fine." I shrugged.

"No, I mean Okay, I'll let you see my pussy again."

"Oh, err, right!" I said. "Come on in then."

"You have to let me watch you jack off this time like you said!" Em sounded suspicious having fallen foul of my play on words many times in the past.

"Yeah, I said you could didn't I?"

"Promise?"

"Yeah, I promise!"

Em finally came into my bedroom and stood looking at me. "Come on then, show me. Take your clothes off!"

"You have to too."

"You first." She replied stubbornly folding her arms across her chest.

"Lets do it together." I suggested. She agreed and we both started undressing, one garment each until we both stood naked facing each other.

My cock had started to grow in anticipation but then I found the undressing a little embarrassing and the prospect of jacking off in front of my sister quite daunting. No one had ever seen me playing with my cock before, ever! I sat at one end of my bed and started rubbing my cock as I stared at Em's pussy. The excitement of it all soon got the better of my nerves and my cock started to thicken and grow rigid. Em's eyes went wide as she witnessed the transformation from short and limp to long and stiff. "Come on, you said you'd diddle your pussy too!" She hadn't of course but I was going to try and encourage her anyway.

Emma frowned, unsure if she had said that or not but she didn't argue and sat cross legged at the opposite end of the bed and began fingering her crack. We continued like this for several minutes, each staring at the other's crotch. I could feel my cum building and increased the pumping action. I was finding the whole experience quite a turn on and was surprised I was ready to shoot my load quite so soon. "Oh god! I'm cumming!" I gasped as my cock throbbed in my fist. Emma leant forward for a closer look just as the first squirt of cum erupted and splashed over my belly. The rest boiled out over my fist as I continued to milk my cock.

"YUCK! WHAT'S THAT?" Emma exclaimed.

"It's called cum." I explained as I mopped up the mess with some tissues I keep for just that purpose.

"Come?" She looked puzzled.

Yeah, spelt C, U, M... cum. And when it squirts out like that it's called cumming."

"Ha, ha... that's silly!" She laughed. "Why has your cock gone all small again?"

"It's always like this." I explained. "It only gets big when I jack off." I was feeling embarrassed now. "Your turn now." I said, pointing at her pussy.

Emma lay back with her legs apart and resumed playing with her crack. I watched intently, taking note of the way she was doing it. Her movements were slow and relaxed at first. Her finger moving in little circles over the little bump thing between her pussy lips. It would be a while before I learned that was called a clitoris. Then she gradually increased the tempo, changing the circular movement to a rapid side to side flicking motion.

"Can I do it to you again?" I asked hopefully. Em didn't reply but moved her hand out of the way allowing me to explore her pussy once more. I spent more time examining her cunt, discovering that her 'bump' was actually a small lump of flesh partially covered with a hood like fold of skin. I then decided to explore her cunt hole. The inside of her pussy felt really weird! I had thought it would be smooth inside but it was soft, warm, wet and strangely lumpy.

My cock had recovered and was just as stiff as before. I was stroking it with my free hand while I was playing with my sister's pussy.

Em obviously liked the feel of my finger inside her. She was pushing her hips off the bed, pushing her pussy more firmly onto my finger. "Push it in and out like this." She instructed as she took my hand and encouraged me to slide my finger deeper into her cunt. "Mmmm yes! Like that, faster, faster!" She panted. Her hand joined mine between her thighs and she continued to rub her bump as I finger fucked her. Then suddenly, just like the last time, she was cumming and crying out as her orgasm struck.

My cock was rock hard again and I was rubbing it purposefully. It wouldn't be too long before my little sister would see me cum a second time!

"Can I touch your cock?" I felt a rush of embarrassment at Em's question but my cock throbbed with unexpected anticipation.

"Yeah, I guess." I shrugged. Em's little fist closed around my shaft. The first time anyone other than me had touched my cock. The feeling was electric! Em was squeezing and stroking it, exploring her first ever cock. I really needed to cum and encouraged my sister to jack me off. "Rub it up and down like this." I moved her fist up and down my shaft until she got the idea and continued unaided. "Ah yes, that's right!" I gasped. "Squeeze it bit harder." I could feel the cum building up pressure and knew I was almost there. "Oh yes!" I gasped. "I'm gonna cum again... do it faster!" She obeyed, copying what she had seen me do earlier.

The rush of cum up my shaft came with the best feeling ever. It boiled out from my swollen tip splashing over my thighs and Em's hand. She squealed and pulled her hand away and I had to finish myself off, milking the remnants of cum from my shaft.

Em was looking strangely at the drops of cum on the back of her hand and poking it tentatively with her finger. "Ew! That's yukky!" She announced.

"Yep... it is." I agreed as I passed her a wad of tissue to clean up.

That was the start of increasingly regular sessions where we would play with each other and make each other cum. We both loved doing it so much and even though we were very scared of being caught, which meant the opportunities were infrequent at first, desire soon made us bolder and we became adept at creating opportunity, sometimes even doing it when mom or dad was home.