This story is intended for people who like a good build-up. It's a mixture of fiction and non-fiction. I will let you figure out which is what, it makes it more exciting. If you've read my previous series, "Porn Session With My Sister In Law" welcome back, and hope you enjoy this series as well.

I’ll start with some backstory. Ali is 28 years old, and recently started a job as a college professor. She has studied accounting and bounced around a few entry level government jobs, never really hitting her stride. She lives with a roommate in a modest condo, spending most her weekends getting drunk with her friends, not giving much care to what her future might look like. Her dating life consists of mostly one night stands, and bad tinder dates. She’s very open about her sex life, often sharing stories to me and my wife. 

My wife is Kate, her older sister. Kate lives a very different life than Ali. She’s a stay at home mom who hasn’t worked in over 8 years. I have been fortunate to be very successful in my business career and therefore have been able to afford a very luxurious lifestyle for my family. 

While Ali spends her weeks working, Kate spends most of them shopping, going to the spa, and her yoga classes. Of course she needs to take care of the kids but they go to school all day. 

There has always been some sort of sibling rivalry between the two. Not that it was much of an even fight. Kate was always better looking than Ali, and certainly more responsible. Which led to them having very different lifestyles. With all that being said, they were still close. Ali came over frequently and I would joke that she was my adopted child because I’d always have to pay for her. 

Ok, enough about that. Now that we got some of the backstory out of the way, we can get into the real story! 

We had planned a family vacation to Panama City to end the summer. Seeing that Ali had not started her new job, we offered if she wanted to come along. It was a win-win for everyone, she got a free vacation from it, and we got some extra help with the kids. This was nothing new for us, she had joined us on a few vacations in the past. 

We settled into our Airbnb and started to plan out how we would spend the trip. I wanted to do nothing more than sit my ass on a beach, drink, and eat some good seafood. The girls had the same idea in mind, especially with the kids. We spent the entire first day at the pool. 

Back at the condo, the girls were talking about how hot it was, and how they definitely didn’t wear enough sunscreen. Kate headed upstairs to shower and get ready for dinner, and Ali headed to her room, which was in the main level. I took a seat in the living room, watching some tv while I waited for Kate to finish showering. Not long after, Ali came out of her room. Still wearing just her bathing suit. Now, here is where I need to add an important detail. Ali’s ass is absolutely huge. She has had a big butt her entire life, playing volleyball since she was young. A few years ago, Ali had put on some extra pounds that made her butt get even bigger, but she had done a good job in the last year shedding some of that extra weight. Her stomach was much flatter, but I swear her ass stayed the same size. This was the one thing Ali had one Kate. And she was very much proud of it. Her bikini was by no means a thong bikini, yet, most of her ass was still exposed. I’d be lying if I said I hadn’t stared at it all day at the pool. 

Anyways, Ali came out to the main room, her bikini top undone, holding the strings in one hand, and in the other a bottle of aloe vera. 

“Mike, do you mind helping me put some of this on my back? I got fried today and don’t want to peel tomorrow.” 

I winced my eyebrow and agreed to help without hesitation. 

“Sure, why not.” I replied, nonchalantly. 

Her skin was warm from the sun, and soft. I lightly lathered the aloe around her back as she held her tits to not let the swimsuit fall off of her. Yes, I’ll admit. Even something as simple as that was enough to turn me on. I couldn’t deny that I was attracted to her, mostly due to her butt. I had been mesmerized by it since the moment I first met her. I got down to her waist, and looked at her ass. It was bright red, with a clear outline of her tan from the bikini being slightly raised. Of course, I wasn't just going to go for it, yet I convinced myself in the moment that it wouldn’t hurt to ask. 

“Do you want me to rub some on your butt too? You got pretty burned” I said, chuckling and as playful as I could. 

She looked back at me with a grin on her face, not a sexual grin, more of a “I bet you would love to help” kind of grin. 

“What? I'm just being nice haha” I defended myself. 

“Fine, my ass did get pretty burned, so thank you” she replied with a still slightly witty tone. 

I got some more aloe on my hand and gently rubbed her ass. My cock got instantly hard, luckily she was facing away from me and couldn't see. I didn't want to make it awkward or obvious how much I was enjoying it so I wrapped it up pretty quickly. As soon as I finished, I did my best to cover my boner with one hand and headed back to the couch. 

“There you go!” I said as I finished. 

“Thanks Mike!” She said as she walked away. The same grin on her face still there. 

About an hour later, Kate came out wearing a very bougie pair of white, beachy see-through pants that accentuated her butt, a cute crop top that hugged her tits just right, with a light sweater draped around her shoulders, and some nice earrings and a necklace. She looked stunning. The funny thing is that she didn’t used to dress like that. Money aside, Kate didn’t have the best sense of style when we first met. I bought most of her clothes in the beginning until she finally started to catch on to what I liked. Still, on most occasions of us going out she ran what to wear by me. 

Ali came out of her room wearing a pink and blue, floral dress. The kind of dress that you would expect to buy at a souvenir shop. It was gaudy, and Kate quickly took notice of it. 

“Is that what you’re going to wear?” She asked. 

Ali looked down at herself, confused why Kate was asking her this. I knew my wife was stuck up, and especially around her sister. 

“Yeah.. What's wrong with it?” she asked, confused. 

Kate winced her eyes, not saying anything. I assume she was trying to think of how to politely tell her that her outfit was not fit for the kind of restaurant we were going to. But to avoid that not being the case, I stepped in. 

“Nothing is wrong with it, it's fine Ali.” I added. 

Unfortunately the damage had been done, and Ali had caught on that she was not dressed up to Kate’s standards. 

“Well, sorry I don’t have the kind of money you have to buy clothes like you. I can stay home if you  want, I don’t have anything much nicer than this.” 

I ran my hand across my face, embarrassed and feeling bad about her response. Kate tried to be nice, but in her usual, sort of condescending way. 

“No honey, it’s fine. If you want, we can do a little shopping tomorrow.” She suggested. 

Ali rolled her eyes. 

“Well as much as I would love to, you may have forgotten that I am unemployed at the moment until my contract starts, and even then, I don’t really have the money for the local shops around here..” 

“It's fine, we can take care of it. You are helping with the girls so I’m sure Mike won’t mind if we help you out with a few outfits, right Mike?” She looked back at me as she said it, as if I had a choice to say no. 

“No, of course not. I don’t mind at all. I actually wanted to pick up some new swim shorts while we were out here, and maybe a new hat so that works out great actually.” I did my best to add in some details so she wouldn’t feel bad about it. 

The rest of the evening went fine, we had a great dinner and some drinks, then called it a night early back at the condo. 

I got to sleep in the next morning, which was much needed for me. I came downstairs and the girls were all in the kitchen getting breakfast ready. Kate was in a cute pair of pajamas, and Ali was wearing a pair of very short shorts, and a white t. I couldn't help but look at Ali’s ass as I came into the kitchen to greet them. 

“How are we doing today?” I asked. 

“Good, feeling rested and ready for the day” Kate replied. 

“Agreed” added Ali, “Feeling much better thanks to that Aloe, thanks again for helping yesterday Mike.” 

I turned beet red, facing away from Kate so she wouldn't notice. Luckily she didn’t seem to pay much attention. Still, I wondered why Ali would bring it up. Maybe I was overthinking it. 

We finished breakfast and started discussing the day. Kate brought up the shopping trip again, and asked if we should all go together or if Ali and I wanted to go alone. The kids didn't want to go shopping, they were ready for the beach. Kate suggested Ali and I just go together and she would take the kids to the beach herself and we could just meet her there afterwards. We all agreed and got ready to head out. 

I wore a pair of lulu shorts and a t- shirt, just something casual. Ali also wore a casual pair of shorts and a tank top. She looked cute, but again, not very… well, high class if you will. 

The shops were walking distance, and they had a golf cart shuttle service that could take you there. We got to the shops and started scoping where to go. 

“Mike.. I’m going to let you take the lead here. First, I feel bad that you’re buying me clothes, and second, you may have noticed I don’t have the best fashion sense. So I’ll let you guide me on what to buy!” 

I chuckled, “Don't feel bad, I don't mind. And just so you know, I had to shop for your sister too when we first met” I shared with her. 

“Oh I knew that, you think we didn’t notice when she started dressing differently?” 

I just laughed. We entered into the first boutique, of course, it was all very beachy wear. Whites and pastels everywhere. I started to look around for her. She had a smaller bust than Kate. Kate had double D’s. And Ali I assumed was about a C. This actually made shopping for her easier. I loved the no bra look, but could never get Kate to go with it, she always said her tits were too big to do that. 

I picked out a few cute tops, some sun dresses, a pair of white pants like Kate had worn, and some cute shorts. 

“Ok, but you’re going to tell me what looks good, right?” She asked, as we headed towards the dressing rooms. 

“Of course” I said chuckling, “This is what I’m good at” I added. 

Ali went into the dressing room and I waited outside of course. Not long after Ali shouted over. 

"Mike? Are you there?” 

“Yeah, I’m here” I replied. 

“Can you go see if they have some strapless bras out there? The one I am wearing is not meant for these and it looks dumb” She said. 

I laughed, “Just don’t wear a bra with those. They are meant to be worn like that” I replied. 

She paused for a minute. 

“Umm.. ok. You’re definitely going to see my nipples poking out of these though.” 

I chuckled even louder. Of course, I was excited about it, but I played it down again. 

“Oh get over it, it’s not a big deal.” I replied. 

A couple minutes later she stepped out. She tried on a light green, somewhat sheer, strapless sundress. It looked amazing on her. She came out with her hands slightly covering her chest, awkwardly showing me what it looked like. 

“Let me see it” I said, “Spin around so I can see it all” 

She removed her hands and hovered them around her sides as she spun around. Still, awkwardly. 

“I need your help clipping the back, there is a little hook I can’t reach” 

I walked up to her as she turned around and held her hair to the side. I clipped her dress and stepped back again to see her. 

“You’re so stiff,” I said laughing. “Let your body really fall into the dress.” 

She looked at me with a smile, then dropped her shoulders finally. Staring directly at me, she started to model the dress. Twirling and putting her hands in different poses. Her sexuality poking through now. And that wasn’t the only thing poking through. I noticed as her nipples got harder just as she began to relax and enjoy herself. 

“Well, what do you think?” she asked. 

She said that just as I was staring at her ass, it took me a second to snap out of it. 

“I love it, it looks great. Get it.” 

“I like it a lot too, ok, let me try on the rest” 

She went back into the dressing room and tried out the rest. I knew the pants were pretty much completely see through, and was dying to see what they would look like on her ass. It’s as if she knew that was the case because she saved them for last. 

“Mike.. not sure I can come out with these” She said nervously laughing, “I definitely did not wear the panties for these and you can see my entire ass..” 

I laughed again, “Ali, those pants are supposed to show off your butt. They are meant for the beach mostly. It can’t be much different than how much your butt was showing in your swimsuit yesterday.” 

“Yeah but today I am wearing a black thong and you can see all of it” She replied. 

“Well then take it off, you can wear that with white panties or without panties, or with a swimsuit..” 

There was a long pause. 

‘Hmm, well, why don’t you just come in here really quick, I don’t want everyone at the store seeing my butt” she called out. 

My heart sank for a second. It wasn’t a very large dressing room, just enough for one person really. I knew I would be pretty snug with her in there, but of course, I wanted to be. 

“Umm, ok. Open up” I said. Walking up the dressing room. 

She cracked the door open and I slid inside. 

The first thing I noticed was her nipples again. They were hard rock poking through one of the tops I had chosen. It was small in there, so we were both standing about 3 feet from each other. I looked down and noticed her panties on the floor. The black thong she had mentioned. I felt my heart start to race, knowing she was wearing nothing but those pants underneath. 

“Well, let me see them” 

She stepped back toward the mirror, facing me. Her hands at her hips. They looked good from the front, but OH MY GOD when she turned around. She may as well not even be wearing pants with how see through they were against her ass. Kate had a great butt, better than most, but as I said, Ali’s was on another level. 

“Damn..” accidentally slipped out of my mouth as she stuck her ass out a bit. 

“I told you they were bad.., this is why I didn’t want to step outside in these” she said laughing. 

I was still trying to catch my breath. She was still staring at herself in the mirror, her ass still facing me as she talked to me. Surely, she knew what she was doing and was enjoying herself too. 

“Yeah.. you might have to wear a swimsuit with those.. Your.. physique is a little different than Kates..” I said, trying to sound PG, and also acknowledging that her ass was bigger than Kates. Something I knew she wouldn’t mind hearing. 

“Yeah.. they look a little different on me than the ones Kate wore yesterday…” She said as she continued to move her hips back and forth, as if she was still deciding how she felt about them. 

Inevitably, I got a little hard. Not full boner poking through but certainly enough to notice if you were looking. We found ourselves in there without saying anything to each other for what felt like a long time, but maybe that was just the tension that had filled the dressing room. She finally broke the silence. 

“Well.. you’re the one buying them so.. If you like them I’ll take them.” 

“I uh… umm..” I couldn’t find what to say next. 

She turned around and looked over at me. Her eyes dropped towards my crotch. She grinned. Just as she had done when I offered to rub her ass. 

“I think you like them too.. So I’ll get them.” She said, before I had a chance to say anything more. 

“Fair enough..” I said. Like an idiot still lost for words. 

“Well, guess I should change back into my clothes so we can get out of here..” 

“OH! Yeah, sorry.” I said, snapping out of it! “I’ll get out” 

“Well, actually, think it's ok if I wear something out? I feel super underdressed in my clothes and would prefer to wear one of these cute outfits. Except these pants haha, I’m not wearing these without white panties at least.” 

“Yeah, I don’t see why not. Just take the tag off of what you want to wear, I’m sure they won’t mind. 

“Ok! What do you think I should wear out? I’ll let you pick.” 

“Hmmm..” I said, thinking about what to pick. “I honestly really liked almost all of it. I guess, the first dress you tried on. I really liked that one, and it's cute, but still casual enough for some more shopping.” 

“Ok! I liked that one a lot too! But more shopping, is this not enough?” She asked. 

I definitely wasn’t used to this. My wife could shop all day long, another clear difference between the two. 

“Oh, well we can be done if you’re happy with this. Should have enough outfits for the rest of the trip, unless you wanted to pick up some new swimsuits. I still have to get a new pair of trunks for the trip.” 

“Oh yeah! Ok, well, just turn around real quick. I am going to change into the dress so you can help me buckle it again..” 

Before I could even turn around, she lifted the top off. She was facing the mirror so she would be able to see if I was looking. I was only able to see her bare back as she pulled it off before I turned around fully. I could hear her taking off her pants. She grabbed the dress hanging from the hook, I turned just slightly and saw her arm reach for it. The thought that she was right behind me naked was driving me insane. I wanted to turn around so badly. I could hear her getting the dress on. I waited a few moments, then turned around a little more, my hand in front of my face as if I was shielding the view. 

“Are you dressed yet?” I said. 

She was bent over, just beginning to pull the dress over her body. I got an amazing view of her ass for a split second, just as she pulled the dress over herself. Thankfully she was looking down, so I didn’t think she even noticed. 

“Just about” she replied. 

I turned back around as she finished adjusting it around her tits. 

“Ok, ready for you to buckle it” she said. 

This time I knew I was in trouble. The moment had me raging hard at this point and I wasn’t sure there was a way to hide it. She held her hair and had her head tilted to the side as I got behind her and buckled her dress. I made sure to take my time doing it. Just as I finished and was looking down, I noticed her black thong was still on the ground. 

“Fuck..” I whispered under my breath. Not even realizing it when I first saw her pulling up her dress. 

I turned around before she could see me, but then realized I had an even bigger problem. I couldn’t just walk out with my cock bursting through my shorts. I paused by the door. 

“Ready?” She asked. 

“Umm… not quite.” I said awkwardly. 

Still facing away from her. 

“What’s wrong..?” 

“Well….” I stammered, “I have a little bit of a situation here that I need to pass before I can go out..” 

I turned my head and looked back at her. She had a confused look on her face. I winced my teeth, showing an embarrassed face to make it obvious. 

“Ohhhh……” she rolled, then laughed, “Was that because of me…” 

I paused. Trying to process her tone. She seemed.. Intrigued at the very least. Without turning around answered, 

“Well yeah… he doesn’t know you’re my sister in law” I said laughing. 

“Turn around. I want to see” she said confidently. 

“No! That’s embarrassing” I quickly fired back. 

“Ok, so I couldn’t be embarrassed about you seeing my nipples poking through or my ass showing but you get to be embarrassed about your boner poking through?” 

She had such a good point that I couldn’t even argue it. Not that I really wanted to. 

“Fine.. you’re right.” I said as I turned around. 

My cock was even harder than it was before, the excitement of her seeing it had me even more turned on. The light fabric on my shorts were hardly holding it back either. If the room was any smaller I would be poking her with it. I faced her and her eyes instantly darted towards my cock. Her mouth slightly opened as she stared at it. 

“Wow…” she let out quietly. 

I didn’t even know what to do with myself in the moment. I just stared at her awkwardly. With the same shit grin on my face that she had earlier. 

“Well… that’s fucking huge” she let out, as if it were nothing. 

She said it so casually that it actually caught my off guard. I choked a little on some saliva before I could compose myself again. 

“Well, thanks!” I said with my hand covering my face in embarrassment, “not as big as your ass but…” I prodded at the fire. 

She laughed, “Yeah well not sure that’s even possible, but yeah, it doesn’t seem to be getting any smaller..” She joked. 

“And thank the good lord for that” I added. 

She blushed, “I take it you like it..? As if she didn't know.

“Do I even have to answer that?” I signaled toward my cock. 

She looked back down again at it. Still blushing. 

“I guess not.. So.. how long does it take for…” she points at my cock, “him to go down..” 

I scratched my head, “well, depends.. But we won’t go there.. Let’s maybe just stop talking about it for a bit and he might go down..” 

She furrowed her eyebrows, and pursed her lips. Not talking for a brief moment, yet, stealing glances over and over at it. 

“Ok depends on what?!” She broke the silence. 

“Ali.. stop..” 

“What? I’m just curious.. Honestly” she replied. 

“Well I’m sure this isn’t your first time being around a guy with a boner… it depends on if I take care of it, or if I stop thinking about it and let it go down on its own..” 

She thought for a second about it. 

“Which one is faster?” 

I couldn’t believe what she was saying. My heart was beating at a thousand beats per minute at this point. I looked back at her face and smiled. 

“Well…. Hard to say. At this rate, taking care of it might be faster since you keep making me all flustered..” 

She smiled back, then made a face that was claiming her innocence in the situation. 

“Me? I didn't do anything. I just put on the outfits that YOU chose for me, remember?” 

God damnit, she had such a good point again. 

“Ok, maybe you’re right on that one too.. I may have set myself up for that one..but I didn’t expect to be inside the dressing room with you. 

“Yeah.. ok, that one was on me..” she replied. “So, are you going to take care of it then?” 

I didn't even know what to say. I just stared at her, noticing how her nipples looked as if they were going to pierce through her dress. 

“Do you want me too..?” I asked. 

She bit down on her lips and looked at me with the sexiest eyes. 

“Is it bad if I say yes..” not breaking eye contact with me as she said it. 

“Is it bad if I say no…” I replied. 

“Do it..” she let out her lips, nearly without sound, mostly sounding it out with her lips. 

It was all the convincing I needed. I reached into my shorts and pulled them down. My cock instantly sprung upwards as the tension from my shorts released. What I didn’t expect was the string of precum that shot in the air as I did so. It would have likely gotten on her dress had it not stuck to my head. The string of it just hung from my hard cock in the air. 

She didn’t break stare on it for even a second. Her mouth now wide open. Her eyes, just as wide. I was so turned on, yet something about the moment had me completely embarrassed. The fact that I was just standing there in front of her with my cock in the air, absolutely drenched in precum. 

“Holy fuck…” she let out. Slowly raising her gaze back up at me. 

I was as red as could be. Terrified at what might happen, yet more turned on than I had ever been. 

“Your cock is seriously fucking huge…. And soaked…” she added. 

I clenched my teeth, “yeah.. I don’t know what to say… fuck..” putting my hand back over my face. 

“Well, are you going to take care of it or…. Do you need..” she drifted off from the sentence. 

I looked at her confused.. “Do I need..?” 

She started fidgeting around. Her hands near her pussy, rubbing her legs slightly. 

“Do you need… me to do it….” she clenched hard on her teeth as the words escaped her mouth. 

Hearing her say that alone could get me to cum, I was dying for her to touch me. I was so nervous I was sure I couldn’t possibly complete a full sentence. 

“Yes” Is all I said. 

She took one step closer to me and reached her hands out and wrapped them both around my cock. One at the base and the other rubbing my soaked head. Her breathing instantly sped up, nearly panting at this point. She wouldn’t look up at me. Her eyes were completely focused on my cock. I got lost in a state of shock. I had imagined a moment like this for so many years that I couldn't believe it was finally happening. 

“Fuck Ali… I’ve wanted this for so long..” I let out. 

She finally looked up at me. She leaned in, and gave me a short, but passionate kiss on the lips. 

“Me too.. Now, can I make you cum…” 

I didn't even speak, I just nodded my head. 

She let go of my cock briefly and turned around. Confused at what she was doing, until she grabbed her hair again and moved it out of the way. She wanted me to unclip her dress. 

I leaned in and undid it. And without turning around, she dropped it off her shoulders. I stared at the reflection of her in the mirror as the dress fell to the ground. Her body completely naked in front of me. I couldn’t resist her any further. I wrapped both hands around her waist and ass as I began to kiss her neck. 

She let out soft moans with each kiss I gave her. Her ass was incredible. I gripped it tightly, squeezing it like I wanted to do the day before and so many times before. She reached her hands back and stroked my cock behind  her back. The head of my cock was pressed hard against her ass at this point. The combination of her hands rubbing it and her ass against it was starting to build me up. I needed to feel her pussy. I needed to see if she was as turned on as I was. 

I reached around her and ran my hands down her pubic bone until finally reaching her lips. As I began to slide my fingers down her slit, I could feel just how wet she was. Her pussy was warm and thickly coated with grool. I reached her opening with two fingers and buried my fingers inside her. 

Her moans grew louder, just loud enough to make me worried that the people outside might hear. The sounds of my fingers inside her pussy might have been louder. She was an absolute puddle and I was loving every second of it. It didn’t take long for her orgasm to arise. She squeezed my cock tight and began to pant and moan. 

“Fuck I’m cumming….” she let out. 

I wrapped my hand around her mouth to cover her moans and pulled her to the side so I could get a better angle at her pussy. She spread her legs for me even more as her orgasm hit her in full force. Her legs were shaking profusely. She threw her head back as I felt her pussy contract around my fingers. She put both hands over her mouth as she moaned deeply into them. Slowly falling into my arms as her orgasm dwindled down. 

Still panting, she looked over at me. Biting her lips once more. 

“My turn..” She mouthed. 

Without hesitating, she dropped down to her knees. Instantly shoving my cock down her throat. She was completely cock crazy at this point. Slurping and sucking on my cock like it was going somewhere. It felt incredible. So good so that I knew I would be lucky to last a minute with the way she sucking on it. 

“Fuck” I moaned, as I felt my balls begin to swell. 

She grabbed the base of my cock and did her best to take as much of it as she could down her throat. Holding it there until she finally gagged and came up for air. I knew she would be good at sucking cock from some of the stories she had shared of her one night stands but I didn’t expect her to be this good. 

“Fuck, I’m about to cum” I let out. 

She didn't stop for a second. She continued to suck my cock as feverously as she was before. I couldn’t last any longer. I began to explode down her throat. That didn’t stop her from sucking for even a second. She continued to slurp and suck hard on my cock, milking every last drop of cum that I had into her mouth. Her mouth felt incredible. The way she swirled her tongue around my head as I continued to fill her mouth with warm cum. I emptied what felt like the largest load of my entire life inside of her. Before I could even begin to wonder what she would do with it she swallowed the entire load. She looked up at me, my hard cock still in her mouth. Cleaning it for me. 

“That was fucking incredible..” I said. 

“Mmm… good. I loved it too.. Your cock is fucking perfect.. I’ve wondered about it for so long..” 

“Fuck, I’ve wondered about your pussy and your throat more times than I can count as well..” I admitted. 

She grinned at me as she got up and started to put her dress back on. “Maybe you'll get to find out what it feels like to be inside me next time..”

I wanted to fuck her so badly in that moment and the idea of a moment like this happening again drove me wild.

I pulled my underwear and shorts back up, and did my best to compose myself. She gathered all the clothes I would be buying, along with scooping her panties off the floor. She looked back over to me, walked up to me and reached her hand out. 

“Here. These are for you to remember our little shopping trip..” 

I took her panties in my hand and felt how they were soaking wet. 

“These are soaked, I thought you took these off before..” I asked. 

“They were soaked from the moment I put that first dress on for you..” 

And walked out…

To be continued…..