I had always known my step-sister was a little different. Little did I know just how different she was, or about a secret my dad and step-mom had been keeping from me.
Our parents were gone for the weekend, leaving us home to fend for ourselves. My 18-year-old step-sister, Mandy, was 4 months older than me, so, of course, she was left in charge. We had been living together since we were both 15 and of course, we had the typical sibling rivalries but got along all right.
"Mandy, you in here?" I asked, knocking on her bedroom door.
"What do you want Nathan?" She yelled.
"My girlfriend is coming over, do you think you can leave us alone?" I asked.
"What? You know Mom and Dad said no company while they're gone," She countered.
"I know, but I'm bored, and she wants to get away from her house for a while," I protested.
"Whatever, just no hanky panky," She laughed.
"Shut up," I scoffed, heading to the front room and waiting for my girlfriend, Caitlyn to get here.
I opened the front door when Caitlyn arrived, giving her a quick kiss before leading the way to my bedroom. "Is anyone else home?" Caitlyn asked, walking into my room.
"Just my stupid step-sister," I replied, closing the bedroom door.
"Oh come, Nathan, Mandy's not that bad," Caitlyn giggled, sitting down on my bed.
"You don't have to live with her," I retorted quickly.
"True, but she was fun to hang out with at school, even though she can be weird at times," Caitlyn giggled again, patting a spot on the bed next to her.
I sat down next to my girlfriend, putting my hand on her leg, "Weird, is definitely what she is."
Caitlyn leaned in and started kissing me deeply, pushing her tongue into my mouth and moaning passionately. I moved my hand up to her chest, cupping her tit and squeezing it lightly.
"Mmm, you don't know how bad I need this," Caitlyn moaned softly, laying back on the bed.
I slid my hand down Caitlyn's abdomen and into her shorts and panties, seeking out her pussy. I pushed my middle finger into her slit, feeling her wetness. "So fucking wet," I groaned, running my finger up and down her slit.
"Thanks to you," Caitlyn cooed, pushing her pussy into my hand.
"Mmm," I groaned, pushing the tip of my finger into her wetness.
"Yes," My girlfriend hissed, arching her back.
Just as I sunk my finger fully into her pussy, there was a knock on my door. "Hey Nathan, do you and Caitlyn want to play a game with me?" Mandy yelled.
"Fuck," I said under my breath. "No, leave us alone," I yelled back.
"Why not? Come on, I promise it'll be fun for both of you, please," Mandy pleaded.
I looked at Caitlyn in disgust, "Why does she have to do that?"
"What kind of game Mandy?" Caitlyn yelled.
"It's a card game," Mandy replied.
Caitlyn and I looked at each other, laughing to ourselves. "Let's entertain her, then we can finish our fun," Caitlyn said.
"You sure?" I questioned.
"Yeah, it can't be that bad. Besides, I don't think she'll leave us alone if we don't," Caitlyn replied.
"True," I said. "All right, Mandy, we'll play your game, give us a minute," I yelled.
"Great, I'll be in the living room," Mandy replied.
Caitlyn and I made our way to the living room, finding Mandy sitting on the floor by the coffee table, a deck of Uno cards lying on it. "Thank you guys," Mandy said, smiling at us.
"Sure whatever," I said, sitting down on the floor across from my step-sister.
"So we're playing Uno?" Caitlyn asked, sitting on the floor to my right.
"Yep, but with a twist," Mandy said, smiling slyly.
"With a twist?" I asked in confusion.
"Yep, each time you lay a reverse, you get to dare the person you reversed it to, to do something, each time you lay a skip card, the person skipped has to remove a piece of clothing, and each time a wild card is laid, the person who laid it gets to dare the other two," Mandy said, shuffling the cards.
"Say what? Not going to happen," I growled, looking at Caitlyn in shock.
"Mandy, we didn't agree to this," Caitlyn protested, looking at my step-sister.
"Sure you did," Mandy said, grabbing her phone and replaying a recording of Caitlyn and I talking to her from my room.
Caitlyn and I looked at each other in shock. "So you're going to blackmail me if we don't play this game with you?" I asked slowly.
"You got it. Remember what Mom and Dad said? So it would be a shame if they found out Caitlyn came over," Mandy grinned devilishly.
'Fuck,' I mouthed, realizing Mandy wasn't joking either. "But you're my fucking step-sister, this is wrong," I protested.
"Ah, keyword, step-sister, so it's not completely wrong; we're not blood-related," Mandy snickered, handing out the cards.
Caitlyn looked at me in horror, before pleading with Mandy, "Mandy, please don't do this. It was all my idea to come over, not Nathan's."
"Too late Caitlyn. I already have the evidence he disobeyed our parent's orders, so come on, let's play. You're first, Caitlyn" Mandy said, picking up her hand.
Caitlyn reluctantly picked up her hand, looking at me in shock. She laid a card onto the discard pile, remaining completely silent.
I looked at my hand, found a card to play, and discarded it. I looked at Mandy with disdain, knowing this shouldn't be happening, but there wasn't any way to stop it.
"What, neither of you had a trick card?" Mandy laughed playfully. She laid a skip onto the pile, and looked at Caitlyn, "Oh look, you have to remove clothing."
Caitlyn looked at me in horror. 'Oh my God,' She mouthed, before looking back at Mandy.
I put my hand on hers, trying to comfort her, knowing there was nothing I could do. "Just take off your socks," I said softly.
Caitlyn slowly nodded, pulling her socks off and tossing them behind her. "Happy?" She scowled at Mandy.
"Geez, so testy, it's a good start, but I hope you get to take off more than that," Mandy chuckled.
I looked over my hand, seeing a skip card, laying it on top of Mandy's. "Your turn to take something off," I growled.
"I see that," Mandy said, her face lighting up. "Well, since I'm not wearing any socks, I guess my shirt has to come off," She smiled, grabbing the bottom of her shirt, pulling it over her head, and tossing it aside.
I tried to stop her, but it was too late, my eyes widening, looking at her bra-covered tits. If I had to guess I would say she is a small C-cup. My cock was fully hard in my pants again, staring at my step-sister's covered tits.
"Your turn Caitlyn," Mandy chirped, breaking my stare.
Caitlyn put a card on the pile, and looked at me with disgust, "Stare harder."
"Sorry, I can't help it, I'm a guy," I retorted in defense. Looking at my hand, I put a Draw 2 card on the pile, "What about this card?"
"Oh Draw 2 means you have to kiss me," Mandy snickered.
"Say what? Fuck no, absolutely not, that is not going to happen, I'm going to pick it up," I yelled, reaching down to grab it.
Mandy slapped the back of my hand and waved her phone in front of me. "No, you don't, or else. Now get over here and kiss me," She growled.
I looked to Caitlyn for help, but she just mouthed, 'You have to do it.'
I swallowed hard looking back at my step sister. I slowly got up, my erection forming a noticeable bulge in my pants, and walked towards Mandy.
Mandy stood up to meet me, looking into my eyes with interest. She grabbed my head with her hands and leaned in, opening her mouth and pushing her tongue into my mouth.
I gagged a little at first, not expecting her to french kiss me, but I couldn't stop her. We both moaned softly. I had to admit, my step-sister was a good kisser.
Mandy finally broke the kiss, smiling at me, "So good."
I quickly sat back in my spot, looking at Caitlyn for her reaction. "That was disgusting," I whispered.
"But hot," She whispered back.
"What?"I whispered.
Caitlyn leaned in closer to me, "You should feel how wet I am right now."
"Seriously?" I questioned.
"Mmm hmm, watching you and sister kiss, was hot. I know you stared at her tits, even me looking at her tits has turned me on for some reason. Plus I can see how hard your cock is. This whole thing is starting to drive me insane with desire," Caitlyn moaned.
I couldn't believe what I was hearing from my girlfriend. I knew she was pretty kinky, and fun in bed. We've been together almost a year and a half now, and we have some wild things in bed, but I had never seen her act like this before. "What is wrong with you?" I questioned.
"I can't help it. I'm so horny right now, I could just fuck you in front of her right now," Caitlyn replied.
"No, settle down," I said.
"Caitlyn, your turn," Mandy said, drawing our attention back.
Caitlyn looked over her cards and threw a Draw 4 card onto the pile. "Is this like a wild card?" She asked, looking at Mandy.
"Kind of, except it involves all of us in your dare," Mandy said, grinning wide.
"Oh my, this could be interesting," Caitlyn said, looking at me lustily.
"Think of something good," Mandy added.
"Can it involve removing clothes?" Caitlyn inquired.
"Only temporarily," Mandy said quickly.
"How about Nathan having to pull out his cock and jerk it in front of us, or we jerk it, while you and I feel each other's tits for a few minutes?" Caitlyn asked.
"Wow, that's good and also really naughty," Mandy moaned playfully.
I couldn't believe this was happening. My girlfriend was being a sex-crazed fiend. It was as if I didn't know who she was.
