[Author's note: The story of how Karen and Colin started a sexual relationship was related to me as a true story. I've added this narrative about what might have come after. It is entirely fictional]
"Mom and Dad are going to be gone the entire day!" Karen said excitedly as she burst into my room.
"Sweet!" I said, looking up at my sister.
I'm 18, and Karen is eighteen months older than me. But even though she's 19, she looks younger. She has auburn hair down her back, a slim build, small but pert tits, and an awesome round ass. She was wearing a short sundress and no bra.
"You know what that means!" Karen said, approaching me as I lay on my bed.
"I was hoping you'd go there," I said, sitting up.
It started out as a kissing game. Karen's friend, Molly, had come over and I "practice" kissed both of them so they would know what boys liked. I was thrilled to kiss Molly and was surprised at how good it felt to kiss my own sister.
When we were alone, Karen and I continued the "game" and found that we were becoming sexually attracted to each other. Kissing led to back massages and me straddling Karen in her nightie. She felt my hardon in her crack and begged to see my dick. That led to manual masturbation, oral sex, and eventually - I entered and came inside her tight hot pussy when my parents were away at a bowling league.
"You know what would be really naughty?" Karen said, tugging on my hand and pulling me up.
"What?" I asked.
"Let's make love on our parents' bed!"
"Ooh, I like that!" I said and followed Karen into our mom and dad's bedroom.
We put a large blanket over the bedspread in case some juice or cum dripped off of us.
I grabbed Karen by the butt and pulled her in, sending my tongue deep into her mouth. She kissed back and our tongues made slurping sounds as we intensely made out. I squeezed her butt cheeks, and she held me by the waist.
"I love you, Colin!" Karen said, breaking off.
"I love you too!" I said. "It's such a dream come true that you want me."
I reached and massaged her little tits, making her nipples harden and stick out of her dress.
"I love that you're not wearing a bra," I said. "I love the feel of your nipples in my fingers."
"Mmm," she said. "I want your mouth on them!"
Karen lifted her arms, and I pulled her sundress off over her head. She was wearing a pink thong and nothing else. Her skin felt so soft as I caressed her chest and stomach, reaching down and running my hand up her panty-covered slit.
"Ooh! Keep doing that!" she purred, holding my hand to her crotch. "I can see you like it too," she said, staring at the bulge in my shorts.
"Who knew a sister and brother could turn each on so easily," I said, grabbing her hand and putting it on my hardening dick.
She squeezed her fingers around my member and rubbed up and down, sending chills through my body. I kept suckling her tits while putting my hand under the waistband of her thong, feeling her bush and wet slit.
"You're growing in nicely," I said, running my fingers through her pubic hair.
She'd shaved for me when I first gave her an oral orgasm, but since wanted to match me so she grew a nice triangle of auburn hair, pointing to her pussy.
"Stick your finger in my pussy, Colin," Karen said, urging me to enter her hole by taking my wrist and shoving it further down her thong.
I turned my hand, so my palm cupped her mound and sent my middle finger into her cunt. It was very warm and very wet. I pulled my finger out and put it in my mouth.
"Now that's a taste I can get used to!" I said.
I kissed and made out with her again, putting my finger back in her pussy and finger-fucking her. Her hips moved back and forth on my finger.
"I've got to take your dick out!" she said, pulling back and tugging at the waistband of my shorts.
I helped her remove them, my dick bouncing out and standing straight out from my body. She knelt and took it in her hands, grasping and squeezing while running her hands down its length.
"Please suck on it!" I said.
We'd only fucked a few times and I was really anxious to get my dick inside her, but I also wanted to take our time and enjoy every sensation.
Karen opened her mouth and swallowed my dick. The warm wet feeling of her mouth on my cock was incredible. She sucked in and pulled out.
"I want to fuck your mouth," I said, holding her head and pushing my dick in and out. "Oh shit!"
Karen came off my cock after a few minutes and stood, helping me take of my t-shirt. I knelt and removed her thong, kissing the little triangle of wet auburn bush and licking up her slit.
"Let's get on their bed," she said, pulling me up onto the king-sized bed.
We knelt facing each other and made out, our hands roaming all over our bodies.
"Want to try that position we watched?" Karen said, stroking my dick.
"The one where I come in from behind? Fuck yeah!" I said.
We'd started watching some porn to get ideas on fun things to do with each other.
Karen swung around and got on her knees, her ass facing me. I came up behind her and started rubbing my dick across her slit, getting it nice and wet.
"Here I come" I said, positioning myself at her opening.
We were still very unsure of what we were doing, but in this position, I found it easier to stick my dick in. It slid right inside. I felt the warm tightness of her pussy grab my cock as it slipped in.
"FUUUCK" Karen said, loudly.
It was still so strange for me to be fucking my older sister. Her body was so perfect and her cunt so wet and inviting. I bent over and squeezed her nipples, holding my dick deep in her pussy.
"Oh yeah," Karen said, starting to pant. "Keep fucking me. I'm so horny!"
I picked up my pace, feeling very good but somehow in control, unlike the first time, when I'd cum soon after inserting my dick.
"Keep ... keep going ... oh, oh, oh!" Karen moaned, shoving her body back on my dick.
I looked down and watched my cock slide in and out. Her perfect asshole puckered and opened and closed as she fucked my dick. I got my finger wet on her juice and started touching her ass.
"Shit, oh!" Karen cried.
I managed to get my finger partially into her asshole and she started squirming and groaning and crying out.
"I'm, shit, cumming! FUUUCK"! she called out as her legs began to tremble and I could tell she was having an intense orgasm.
As she came, I wondered what it felt like for a girl. It seemed to consume her body as she thrashed back and forth on my dick. She laid her face down on the bed and panted.
"Shit that was good!" she panted. "You didn't cum?"
"Not yet," I said, still going slowly in and out of her pussy. "I was so enjoying watching you, and ..."
"And?" she said breathlessly.
"What would you think about me putting it in the other hole back here?"
"In my asshole?" Karen said, turning her face to the side and looking at me.
"Yeah. It looks so good!"
Karen thought for a moment. "I'd never thought of that, but it sounds good, as long as you do it slowly."
"Oh, I will," I said.
I withdrew my dick from Karen's pussy. It made a squish-squish sound as it came out. My dick was drenched in her juices. I lifted it up slightly with my hand and pushed the head against her asshole.
"Just relax your ass," I encouraged. "That's it, you're opening up to me. It's tight. So tight!"
I pushed a little harder and suddenly the head of my dick popped into her asshole.
"Fuck!" Karen said. "Fuck! Keep going. It feels weird ... but good."
"Okay," I said, and pushed in some more.
