My 21-year-old girlfriend Mandy and I have been going out for a little over six years now. We’ve lived together for about three of those six years. Mandy is a beautiful girl, 5’ 3", 95lbs, blonde hair, brown eyes, and a body that gets attention everywhere she goes. Our relationship is wonderful and our sex life is fantastic. I’m sure that we’ll end up getting married some day, I really love her.

Mandy has a younger sister named Alicia. I remember Alicia as a little girl; 13 years old, playing in the front yard while I was trying to seduce her older sister in the house. An annoying little pigtailed brat always wanting to go with us to the movies, always seeming a little jealous of me and yet still wanting to impress me. She was such a cute kid. Alicia is 18 now and she’s turned into quite a good-looking young lady. She’s several inches taller than Mandy, with brown shoulder length hair and a bit more of a figure – a bigger bottom and bigger chest.

About six months after Mandy and I first moved in together, Alicia began having some serious problems at home. The girls’ parents were divorced and they ended with their father, so Mandy had become the de facto mother in the family. When Mandy moved out it really seemed to upset the balance at the house. Alicia felt that she was now old enough to make her own decisions. Their father was fairly strict and let her know that she would follow his rules as long as she lived under his roof. She started missing classes at her high school and her grades began to suffer. I heard all of this from Mandy. Every few days she would give me an update on the situation. It seemed like half of the conversations that I had with my girlfriend revolved around her little sister.

Things came to a head in March of that year. Alicia was getting close to the end of the semester, but her grades had slipped so far that it was becoming a real possibility that she might be held back. Things between her and her father came to a breaking point. He threatened to kick her out if she didn’t straiten up and she threatened to run away if he kept being mean.

Mandy was waiting for me to get home from work one Friday. She was obviously unsure of herself as she approached me. "Um, I have to ask you something. It’s really important to me. Please don’t be mad. Promise?"

"I’ll try my hardest." I answered, not sure what was coming next.

She continued, "I want Alicia to move in with us for while. Just for a couple of months, until the end of the semester. She already has plans to spend the summer with our aunt in Chicago, and after that…"

"Mandy," I interrupted, "We just moved in. We’ve barely had any time alone together, away from both of our families, and everyone else. I don’t know."

She bit her lip. "Please. I talked to her about it and she’s really excited. She promised to be good. She just needs some time away. She’ll go to school if we let her stay here, and we’ll work out a list of rules, and it’ll only be for a little while. Please."

"If it’s that important to you. If you promise she won’t be a pain in the ass. Okay." I gave in.

Mandy was ecstatic. She kissed me and ran for the phone. That Sunday, two days later, Alicia moved into our place. She didn’t bring much with her, some clothes and a couple of ragged stuffed animals.

To my surprise, everything went well with the new living arrangement. Alicia slept in the living room of our one-bedroom apartment on a couch that folded out into a bed. She kept her promise to Mandy and began going to classes again and she even helped around the house occasionally. Alicia and I actually became friends, too. I would talk to her about my life and listen to her stories about how shitty it is to be so young and how great life is going to be in the future and all the rest of it. The three of us would go out shopping together, rent movies, and hang out. Mandy was so happy with the way things were turning out. She had her sister back, and her boyfriend was okay with it. She thanked me just about every day for helping Alicia out.

One thing that I learned about Alicia was that she really liked to sleep in. On weekends she would sleep all day if you let her. Sometimes, for fun, Mandy and I would get up on Saturday morning and run in and jump on Alicia’s bed, picking on her and annoying her until she woke up. Eventually, she would come out of her sleep-induced state of grumpiness and we would all go down to a café a few blocks over for breakfast.

One Saturday morning in late April, I woke to find Mandy hovering over me shaking me. "Let’s go get Alicia." She giggled, showing me that same evil smile she used to give me when we would have tickle fights and she would win.

"Sheesh, let me open my eyes for a second and focus." I grumbled.

Mandy wouldn’t have any more of me sleeping, she reached down and pinched me on the inner thigh.

"Fuck! Ow! Okay, okay, you win. I’m awake." I said for my own safety.

She dragged me out of the bed. I was wearing a T-shirt and my boxers as that’s what I always slept in. She led me into the living room where Alicia was sleeping very soundly, with the covers pulled all the way up over her head.

"Let’s get her!" Mandy ordered as she bolted for the bed. I followed her lead and soon enough we were both on the bed tickling her little sister through the blankets.

Alicia woke up slowly and reluctantly. "Leave me alone, please." She begged.

Mandy certainly wasn’t going to leave her alone. She kept at her, poking and pinching and prodding. Eventually the two got into some argument about sleep and how much of it you need. Laying on the edge of the bed I decided to intervene, "Okay you two, no fighting."

They kept at each other. Both of them had taken on the "sister" tone that I knew so well. They were both always right when it came to these kinds of arguments. They could go on forever.

"Enough," I said, starting to get annoyed. I grabbed Mandy and pulled her playfully away from Alicia. Then I steamrolled over her and landed right between the two of them. I glanced over and saw that Alicia looked angry, like a hurt little girl who wanted to win but didn’t.

"Okay, you two are going to remain separated until you can promise me you’ll get along." I said, faking a deep father voice.

"Okay daddy, we’ll be good." Mandy mocked.

Alicia unexpectedly laughed at Mandy’s joke and I laughed at how stupid the two of them had been. Everything seemed to be cool again.

As I lay there in the center of the bed I noticed that the mattress sagged quite a bit in some places.

"This bed bothers my back, how has it been for you Alicia?" I asked.

"It’s okay." She responded, "Anything is better than where I used to be. I’d rather sleep on a rock than go back there."

"This feels almost as comfortable as a rock, to me." I said, "It’s making my back ache."

"Poor baby," Mandy mocked again, "Roll over on your side and let Dr. Mandy look at it.

Never one to pass up a back rub, I quickly rolled over on my right side so that my back was accessible to Mandy. I was also looking right at Alicia. I smiled and she smiled back. I began to purr as Mandy moved her hand around my shoulders and neck.

"No fair," Alicia jealously chimed, "I’m the one who sleeps in this bed all night every night. If anyone deserves a back rub, it’s me."

"All right, all right," I said, "I’ll rub your back as long as your sister keeps rubbing mine."

Alicia rolled over onto her side, facing away from me. I pulled the covers down her back a little and began to rub her shoulders. She was wearing a black lace bra and the strap ran across her back just below her shoulder blades. She began cooing as I dug my thumbs into the muscles of her upper back. I used my hands to unknot her sore shoulders, being careful not to make marks on her soft skin.

A few minutes later, as I was still working on Alicia, I felt Mandy stop kneading my back.

"Hey!" I protested.

"You got your fair share," She answered. "I’m getting hungry, it’s almost 11am. I’m going to take a shower and then we can go out to get some breakfast." She climbed off the bed, walked back to our room, got her shower supplies, and headed for the bathroom.

"Well, shit." I said to Alicia.

"Come on, you just started on me. Give me a few more seconds, at least." She begged.

"Okay, okay." I replied, knowing we had at least 10 minutes to kill before Mandy would be out of the shower.

I went back to rubbing her shoulders and neck as she breathed in and out deeply.

"Now my lower back," she pleaded.

I pulled the blanket down further off her bare back. I put my hands on the middle of her back, just below the bra strap, and began to massage her.

"No, lower." She begged.

I moved my hands down lower, right to the edge of where the blankets stopped, to the small of her back. As I started in again on her muscles I heard the water turn on from the shower down the hall.

"That feels really good." Alicia offered, "Try it even a little bit lower down."

"Uh, that’s about as low as I can go." I said, slightly embarrassed. If I moved the covers any more I was afraid I might cause her to feel uncomfortable.

Alicia reached around behind her back and grabbed the covers with one hand. She pushed them far, about half way down her thigh. I was in shock. I looked down at the area of her body that had just been exposed. She wasn’t wearing anything from the waste down. I suddenly felt my hands begin to tremble.

"Okay, now go lower." She laughed.

"Um, okay." I said, nervously.

I moved my hands down a little more, to the very bottom of her back, almost the top of her butt, and began rubbing again. As I looked at my hands I couldn’t help noticing how nice her ass was. She had perfectly shaped golden cheeks with no tan lines at all. I tried to ignore what I was seeing, but I knew that my dick was starting to wake up. I decided the best thing to do was to get out of the situation as soon as I could. I stopped touching her back.

"Hey!" She said, "What are you doing?"

"Your time’s up." I said, scared and ready to run for my room.

She didn’t respond. Suddenly I felt her hand on me. She’d reached down between her own legs and put her palm on the front of my shorts.

"It’s your turn now," She said seductively, "and it feels like you’re more than ready."

She was referring to the rock hard erection that had developed in my pants as a result of laying a few inches away from my girlfriend’s nearly naked teen sister. I tried to hard to resist.

"Stop, Alicia." I attempted to sound forceful.

Alicia was done talking. She grabbed the waist of my boxers and pulled them down and out of her way. She squeezed my dick a few times and then pulled on it, at the same time sliding her body toward mine. In a split second, without me moving a muscle, my hard member was between her legs. I felt warmth from her crotch and her soft hair rubbing against the tip of my dick. She pushed further back against me and moaned. The end of my organ was already inside of her. I grunted, not sure what to do. I felt pleasure pulsing through my body.

She began to rock back and forth, moving the tip of my dick slowly in and out of her pussy. I couldn’t take it anymore. I wrapped my arms around her, pulled down her bra, and grabbed a hold of her firm c-cup tits. I thrust my hips forward, finally burying my shaft deep inside of her. Alicia moaned louder. I pulled back and then thrust hard again. She was so tight I could feel every inch of myself sliding in and out of her. She was breathing heavy as we moved back and forth against each other.

I wanted more. I wanted to be deeper inside of this young girl, but the position wasn’t right. I grabbed her waist and pulled her toward me. Then I rolled her over onto her stomach and pulled her ass up in the air. She understood and folded her knees under herself. I now had her in doggy style position. Her firm round ass was sticking straight up, waiting for me. She reached her hand around and grabbed my dick again. She put the tip of it right against her opening. I rammed it in as hard and fast and far as I could. She made a loud noise, I couldn’t tell if it was pain or pleasure. I wrapped my arms around her flat stomach and rested my entire weight on her back as I began to fuck her. I fucked as hard as I could, pulling all the way out and then slamming forward, burying myself down inside of her all the way to the base of my thick shaft. I hammered violently away at her, knowing that I didn’t have much time before my girlfriend would be out of the shower. I had never fucked someone so hard and so fast in my entire life; it was like we were animals breeding, not people. I wasn’t sure if I was hurting her she liked it, but she'd wanted me and I was giving her everything I had.

Suddenly I was coming. My eyes rolled back in my head as I shot a huge load of come deep inside of Alicia, pushing myself as far as I could into her hole.

I opened my eyes. I’d pushed so hard during my orgasm that I knocked her flat down on the bed and I was laying on top of her with all my weight. I stayed there for a few seconds, feeling her soft young skin against mine, listening to her heavy breathing, and taking in the smell of her hair.

Alicia broke the silence, "You’d better go to your room and get cleaned up, silly. Mandy will want us to be ready for breakfast soon."

"Yeah, um, okay." I stammered as I pulled out of her and climbed off the top of her.

"Thanks." She whispered.