I used a prompt from r/dirtypenpals by user cgburner titled "Your best friends sister secretly craves your cock" the prompt ended with the best friend Reiner telling me I could try to go upstairs and talk to his sister.

I didn't know what the OP looked like so I used the photos from user bendybo. Who is really pretty gorgeous.

Thoughts and comments are appreciated.

Reiner's Little Sister

I sat there mulling over what Reiner just told me about Stacey. The controller in my hand felt heavy and my focus went hazy.

-Uh hello?

-Oh Sorry. Yea not going up there.

-Whatever. Just being informative.

-Look, best case scenario we have sex and it will be forever weird between all three of us. Worst case scenario she freaks out and it is weird between all three of us. I don’t see anyway weirdness doesn’t happen.

-Keep talking about it and it will be weird no matter what.

We kept playing but my concentration was shot and the story Mark just told me hung heavy in the air. Small talk seemed non-existent even though we both tried to change the subject. After an hour or so I decided it was best to go home and hope that the next time we hung out it would be less weird. Because fate is a cruel bitch I ran into Stacey at the top of the stairs. She looked up at me and then down quickly at the ground.

-Hey Stace.

-Hi.

She mumbled softly. Even in sweatpants and a t-shirt she looked gorgeous. Straight dark hair falling just over her eye. I think I saw her smile as she looked at the ground. I turned to walk away but not before she glanced up and we made eye contact. Our eyes held each other a split second longer than necessary and the electric between us could power a small city. I was standing awkwardly now; my body and head in opposite directions. This was too much and I had to leave quickly.

-Well. See you around.

-Hope so.

I rushed out of the house with Stacey’s “I hope so” buzzing in my head. I went home and locked myself in my room. I immediately went on Stacey’s facebook page and jerked off while flipping through her photos.

In the coming days I hung out with Reiner and things between us were fine. We never brought up Stacey again and I purposefully stayed away from his house. The fantasies wouldn’t stop though. I played over sexual scenes in my mind; each dirtier and more elaborate than the next. Stacey became an itch that I just couldn’t scratch.

Reiner went back to college for pre-season in August. I waited for a weekday when I knew Stacey was likely home alone. With my nerves at an all-time high I knocked on the front door. No answer for what seemed like an eternity so I knocked again. I was almost positive she was home. I peaked in the side window but it was way too dark to make anything out. While cupping my hand on the window I heard the door open suddenly.

-Hey.

-Oh hi Stace. Sorry I wasn’t sure if anyone was home.

-Just me.

She was wearing the same light sweatpants as the last time I saw her but this time she had on a sheer tight tank top and by the site of her erect nipples she wasn’t wearing a bra.

-Oh. Where’s your brother? I sent him a text but didn’t hear back.

-He already left for pre-season.

-Ah that sucks. I wanted to wish him luck and get back my FSU shorts he borrowed.

-Well you can come in and check if you want.

I brushed past Stacey purposely putting my hand on the skin of her lower back. I looked down into her eyes as I did so and traced my index finger around her waist letting linger until I walked away. I could see her inhale sharply and cast her eyes down to the carpet. I quickly walked into Reiner’s room and did a brief check for my shorts that I knew wouldn’t be there. After checking for what I felt was the appropriate amount of time I went back to see Stacey still standing by the front door.

-I think he might have left them in the basement.

-Oh let me…

I walked down the stairs to their family room and noticed the tv was on pause. Onscreen was a naked Elizabeth Berkley. I slowly stepped into the room and turned back to see an aghast Stacey with her mouth open. Not sure how to make her feel comfortable I blurted out:

-Is that the chick from saved by the bell?

Stacey nodded a slow yes.

-Wow. I’ve never seen this. Can I watch?

-I guess.

I sat down on one end of the couch and Stacey took a seat at the other. She pushed play on the remote and we sat in silence as Elizabeth Berkley and another woman made out on screen. We watched for a minute or two before I asked to see it from the beginning again. Stacey rewound the scene and let it start again. We watched these two naked women on screen before I turned to my best friend’s little sister:

-Guess we’re not in Bayside anymore.

Stacey laughed and looked over at me. Our eyes locked in and I could feel the chemistry between us.

-I don’t know how you can watch this and not masturbate.

Stacey’s eyes went down and she blushed noticeably.

-Oh! Is that what I interrupted?

Stacey bit her lip as she smiled; that gave me my answer.

-Hey no judgments. Look I’m half erect from just that scene now.

-No kidding.

Stacey kept her eyes on the bulge forming in my nylon shorts. She stared while I gave it a soft tug over the material; straitening my hard dick and making it more noticeable through the shorts. Stacey bit her lip again. Feeling daring I leaned back on the couch and spread my knees. I continued to rub myself over my shorts. I looked over at Stacey who was eyeing me like a predator does their prey.

-Have you ever watched a guy jerk off before?

-No. If I see a dick I think I know what to do with it.

-Look at you. All grown up.

-Seems you’re doing a bit of growing yourself.

-Want to see how much?

-I do.

I lifted my hips off the couch and slid my shorts and boxer briefs to the ground. The excitement of Stacey looking at my erection meant I was rock hard. I lifted my t-shirt over my head and sat on the couch naked next to my Reiner’s little sister. I started to stroke myself slowly. Looking over at her eyes I asked:

-Are you going to let me masturbate alone?

-That’s what I was thinking.

-Well, If you were going to touch yourself to Elizabeth Berkley on tv I would think you would like touching yourself to a live show from me. Or maybe you only like girls?

-I like guys…

-So then why don’t you pick up where you were when I interrupted?

Stacey reached down between the cushions and pulled out a pink plastic dildo. My heart began beating even faster as she slipped it under her elastic waistband. I could hear the soft sounds of vibrations and see the tension in Stacey’s shoulder dissipate. I continued to stroke my hard cock careful not to get too excited too soon.

-Does that vibrator feel good?

-uhuh.

-Is it inside you or just on your clit.

-It’s in my pussy.

-You don’t like it on your clit.

-I have my fingers on my clit.

Holy shit was this hot. A writhing Stacey only feet away from me.

-Are you going to show me how you do that? It’s not fun hiding under those pants.

-Noooooooooooo.

-Really? Should I put my shorts on and touch myself like you?

-Oh no. You’re fine as you are.

-So you like to see me do this?

-Obviously.

-Well isn’t it better to watch me do this naked? And wouldn’t it be better for me to watch you do this naked?

Stacey looked at me and rolled her eyes. She removed her hands and pink plastic vibrator from her sweatpants. Still holding her toy she stood and pulled down her sweatpants bending over to give me a great side view of her naked ass. Stepping out of the pants she sat back on the couch but this time she turned and leaned back facing me. She lifted one leg on the couch and gave me a perfect view of her shaved pink pussy. She turned the vibrator back on and rubbed it on her clit.

-You look amazing.

-Thank you.

I turned towards her and leaned back as well mimicking her pose. I was still stroking at a slow even pace but it was getting hard to delay the oncoming orgasm. Stacey inserted the vibrator in her wet open cunt and fucked herself rhythmically.

-Do you touch yourself often?

-Everyday. Just usually not with my brother’s best friend.

The mention of Reiner turned me on even more and I wanted to push it.

-You think he would be mad about his best friend watching his sister get off?

-I think he would want us both to be happy.

-Are you happy then? What else can I do to make you happy?

-Cum in my mouth. Let me taste my brother’s best friend.

I couldn’t stand it and I began to stroke faster. I stood up to give her full view of my naked body.

-You want to see me cum?

-Yes I do. I want to taste it.

I walked over to her and rubbed myself near her face. She increased the speed and tempo. Fucking herself furiously she increased the speed on her clit. She sat up to get even closer to the engorged head of my cock.

-I’ve known you since you were 8 years old and you want to taste my cum?

-I’m 18 now so do it. Shoot your cum in the mouth of Reiner’s sister. Show me how you make yourself cum.

I was on the verge and leaned over Stacey carefully placing the tip of my dick on her lips. She licked it before wrapping her soft wet lips around the tip. She slowly took more in and I could feel her tongue licking the underside of my head. I was pumping my hand and could feel the swelling of an orgasm.

-I’m going to cum Stacey! I’m going to cum in your mouth!

I could hear a muffled moan and the vibrations from her mouth sent me over the edge. I exploded emptying myself down her throat; my semen hitting her mouth must have been what she needed because her eyes rolled back into the back of her head and her shoulders started shaking uncontrollably. My own orgasm subsided and Stacey removed her mouth from my cock. She let out a garbled guttural moan as wave after wave of ecstasy passed over her.

-Wow. If I knew it would be like this I would have gone right upstairs as soon as Reiner told me…

-Told you what?

-Oh fuck.

[edit: formatting and I changed the brother's name by request]

Source: reddit.com/r/sexystories/comments/2vnnsm/marks_sister_stacey_mf_mast_oral