The next afternoon Brian, Ella, and I wait in the parking lot of Tractor Supply as my girlfriend pulls up. She gets out of the car and I make introductions “Brian, Ella, this is my girlfriend, Lexi”. Lexi is about the same height as my sister, though her body type is far different. Where I would describe my sister as tight and toned, my girlfriend is curvy and voluptuous. They all greet each other and I ask “Okay, we are here now, so what are we doing at Tractor Supply?”

“First lesson, Davy”. My sister smirks. “We are going to teach about ropes, so we first need to get you some ropes, and the ropes from here are way better than the cheap ones on your average BDSM website or some shady sex shop. These can actually stand up to a little struggling” 

Lexi and I looked at each other. She smiled and seductively raised an eyebrow as we followed Brian and Ella inside. We quickly made our way to the area with ropes, chains, and other tie-downs and Brian, once sure no one else was around, began with his ‘lesson’. “The first thing you should consider about a rope is how thick it is,” he said as he picked up a colorful strand looped around a spool. “This can affect the safety as well as the feeling it gives. A thin rope can apply more pressure which will give it more of a sensation and make it leave more of a mark. The problem is that this same pressure can also cut off circulation. You have to be more careful with thin robes because they can more easily cut off blood flow and possibly cause damage” he said matter-of-factly, sounding very much like a school teacher. My sister playfully grabbed Brian’s crotch and gave it a provocative rub. “Small ropes, or even things like paracord for shoelaces are very good at making precise ties or binding up sensitive bits, as long as you are careful with the pressure like he said” she added as she gave is cock a few strokes under his pants. 

“Also good at creating a crotch-rope with some bite,” Brian replied with a cough, trying not to be too distracted by his wife.

“I prefer a thick rope with some knots” my Ella shot back. 

Clearly relaxing into, and enjoying their role as teachers, my sister and brother-in-law were eagerly explaining other aspects of selecting robes. They talked about material types, lengths and other aspects. Lexi was eagerly lapping up the information, she had always been the more studious of the two of us, while I was somewhat listening but also daydreaming about what Lexi and I might be doing with ropes later. “Hey Davy, pay attention, there is going to be a test later!” my sister said with a smirk, pulling me back to the moment. She was not entirely kidding about the test though.

Brian and Ella answered some questions from my girlfriend and I, helped us pick out some ropes, and we checked out with our newfound toys. As we were about to leave, my brother-in-law seemed to have an idea and ran back inside, soon emerging again with a newly purchased riding crop. He and my sister smiled at each other as he tested it with a good swat on her jeans-covered ass. 

“Okay kiddos, part two of this lesson at home” my sister said. She looked over at my girlfriend, “Lexi, did David tell you what to bring?”

“He did” she acknowledged. “I decided on a one-piece swimsuit”. I squirmed a little as she said this. Lexi looks amazing in the high-cut one piece she has. It further accentuates her already great hips. 

“Perfect,” my sister replied. “David, do you have either some kind of tight swimsuit or underwear?”

“Boxer Briefs.”

“Okay then, see you two at home.”

I had ridden to the store with Brian and Ella, no point in taking two cars,  but this trip I rode home with my girlfriend. At first we did not say anything at all. I think both our minds were racing and we were some mix of nervous and excited. Finally, Lexi was the one who broke the silence “David… are we really going to do this?”

“If you are still okay with it. I think I am over how awkward I felt at first, take a look” I said, pointing at my pants, from which my cock was clearly trying to escape. 

She saw my growing problem and smiled. “Okay, so I am not the only one turned on, despite the circumstances”. With that she took my hand with one of hers and pulled it over to her. Trying to concentrate on her driving to guide my hand between her legs and I got the gist enough to continue on my own. She had worn a dress over leggings, one of her favorite combinations and as my hand slipped under her dress and up her leg, I could tell just how turned on she was. Her leggings were soaked at the crotch and I could not help but start to rub her through her clothes. She let out a sigh of pleasure “dammit … wait David just wait”. She cursed and pulled my hand away before returning both hands to the steering wheel. 

Luckily it was not a long drive into the suburbs to my house and no sooner had she parked the car in the driveway did Lexi lean over and unzip my pants. With practiced skill she took my cock into her mouth and began swirling her tongue around my head. I moaned and reached over to once again put my hand up her dress. She accommodated by lifting one left, placing it over the steering wheel, allowing me easy access to reach into her leggings. To my surprise she was already wearing her one-piece underneath her leggings, so I pulled that aside and my index finger quickly found her clit. She moaned around my cock and began to bob her head up and down as I drew circles around her clit. She must have been especially turned on, and her clit particularly sensitive because it took almost no time before she cried out to mark her orgasm, though her lips never left my cock. After coming down off the orgasmic high, she repositioned herself and went absolutely wild on my cock. Mouth, hands, and tongue all worked in tandem and it felt like no blowjob she had ever given me before. Soon I exploded into her mouth, calling out her name as I slumped back in my seat. She swallowed my load and sat up, looking very pleased with herself. “God I needed that” she sighed. “I have been thinking about it constantly since last night”. 

Still breathing heavily, I slowly composed myself. “Oh my god Lex…”

“Mhmmmm, I know. More where that came from, I am still horny as hell.” It seems she may have been more into this idea than even she had realized. “Let's get in there and not keep your sister and brother-in-law waiting”. 

We walked into the house where my sister was waiting with her signature knowing smirk. “Well, now that you two finally decided to get out of the car, we can move to part 2” she quipped. “Hand me the rope you bought, go change, and then meet in mom and dad’s room.”

“No need.” Lexi replied. “I think we are both already wearing what we need.”

“Well then follow me”. We followed Ella to my parents bedroom. There Brian had already begun laying out their own rope collection on the bed. It was extensive, far more than I had seen last night. They had robes of several different colors, thicknesses, and lengths, all neatly situated and arranged on the bed. As we entered and handed over our new rope, Brian showed us how they tied their rope for storage in a way to prevent damage and tangling. Ella arranged our ropes beside their collection and then, putting her hands on her hips as if psyching herself up to the task, she asked us “Okay, you two ready?” 

“As ready as I can be…” I said with a slight hesitation while Lexi simply nodded. 

Ella looked at her husband and shrugged with a ‘too late to turn back now’ kind of expression and they both stripped down to their underwear. My sister was wearing a very tight pair of boy-short style underwear and a sports bra, Brian was wearing what looked like very expensive boxer-briefs that did very little to contain his erection. My girlfriend and I followed suit, with her stripping down to the one-piece she had worn under her clothes, and me down to my usual boxer-brief. With everyone down to their skivvies, we all took in an eyeful of each other. 

“Okay beautiful people” my sister broke in “which one of you is the submissive?”

Lexi and I just looked at each other. We knew what that meant, but we had not really figured out which, if either of us, was submissive. 

“Maybe you don’t know, or maybe you are switches?” My sister inquired. “Which one of you fantasizes about getting tied up?” We both raise our hands. “Which one of you fantasies of tying the other one up?” Again, we both raise our hands. This actually seems to make my sister happy. “Okay, so either you are each a switch or you have not played around enough to figure out what side of the coin you fall on. That’s fine, we can work with that. Brian and I switch so maybe we will just do a round of each person being the one tied up”. 

With that Brian picked up some rope and very clearly said “Okay then, ladies first”. 

Ella smiled at him and very sweetly replied “Yes, Sir.”

Brian walked us through the tie he was going to be showing us, a karada or full body harness. He helped me pick out ropes and had Ella and Lexi stand on the carpet with their legs shoulder-length apart. Ella assumed a very submissive looking pose, with her hands behind her back, and head down. Though we were not told it was necessary, Lexi mimicked until Brian commanded her to look up so she could watch him work. He showed me how to find the center of rope and make the first knot, creating a loop that would anchor around the neck. He explained we should always start going down the front so that future tension would be on the back of the neck, rather than the windpipe. He showed us how to make knots in the rope at various intervals down the chest and belly, each of which would anchor future parts of the harness. “And now for Ella’s favorite part” he said, tying a knot slightly larger than the others. “This one is not for any anchor points, but will rub on her clit. You may need to make adjustments to make sure yours is in the right spot” he said as he finished the knot, ran it under my sister’s crotch and pulled it tight, causing her to sigh in pleasure. It took some time, but I eventually tied one at the right spot in the rope to hit Lexi where she enjoyed it. 

 Brian worked his way through the rest of the karada, forming an intricate diamond pattern down Ella’s body, as I copied on Lexi. Once done with the body harness he moved on to an extension that would bind the wearer’s hands behind their back. Through all of this Ella had been purposely squirming, seemingly to take pleasure from the knot between her legs. Brian had given her several swats on the ass and told her to stop being a brat to which she always replied innocently “sorry, Sir”. It always sounded more sarcastic to me than genuine, though they both had smiles so I assumed it was part of their own game. For her part, Lexi also squirmed, but I think it was more out of pure hornyness than from trying to get something out of the knot. 

Once both ladies had their arms bound behind their back, a full harness running from their neck to their crotch, Brian declared that was probably good enough for a first time. Ella seemed disappointed “what no leg ties?” she asked.

“Don’t make me gag you…” Brian replied.

“Oh no… don’t gag me, Daddy .” Ella said. She put almost no effort into the words, feigning concern until the last word, to which she put great emphasis and had a devilish grin as she said it. 

“God dammit…” Brian muttered. 

Ella’s grin only widened as she continued “Please don’t be mad with me, Sir. I would hate to be punished by you, Daddy.”

Brian turned to my girlfriend and I “Hey, I don’t want to scare you two off, this is supposed to be educational, and Ella wants that too…” he said even while my sister was pushing her ass back into his crotch.  “But she is also clearly trying to provoke me and knows my buttons…” my sister looked at us with a feigned, innocent-looking smile and shrugged. “We can continue in a few minutes if you two want to leave, but I NEED to fuck her, right… now...“ 

Lexi and I looked at each other, both of us having long since gotten over any embarrassment that may have come with the circumstances. “David already got to see you two fuck. I think it is only fair I get to” Lexi spoke up. 

Ella smiled widely, clearly not having been kidding about being an exhibitionist, and Brian wasted no time. He was just over 6 feet tall and had no trouble moving my sister wherever he wanted. Picking up Ella, he roughly threw her, face first, onto the bed. “God yes! Please fuck me Daddy!” my sister exclaimed as he took her by the ankles and pulled her back so that her crotch was at the very edge of the bed. Brian pulled down his boxer-briefs, releasing his raging erection and pulled aside the knotted rope running between my sister’s legs as well as her underwear. He grabbed her by the rope harness and began fucking her, even harder that I think he had last night. 

As Lexi and I watched, she began to squirm even more, pushing her ass back as she did and rubbing it against my still clothed cock. I honestly had not been all that hard throughout any of this so far, as I was more focused on learning the rope technique than the sexual aspect of it. But now I was quickly becoming erect. Between my sister getting fucked before my eyes, moaning like a whore, and my girlfriend, tied up and nearly helpless, but still pressing herself into me, I just couldn't contain it. 

I slowly walked us backwards, to one of the armchairs in the room that faced the bed. I sat down and pulled Lexi into my lap. I ordered her to put her legs over the arms of the chair, spreading her wide open. My sister would have gotten a clear view of her wet, swimsuit clad crotch, though she was very occupied at the moment. I reached between my girlfriend’s legs and once again found her clit. Using both my fingers and the knot of the rope I began to rub her, eliciting moans and gyrations of her hips. While she could move her legs, there was not much else she was capable of in her state and I felt a new sensation as I pleasured my nearly helpless girlfriend. 

At some point during their frantic lovemaking, Brian had seen where we had moved to and, without ceasing his thrusts, he took my sister by her hair and made her look up at us. “Look over there. Your brother and his girlfriend are getting turned on watching you be fucked. He is fingering her right now while I fuck you. I bet you enjoy that, don't you?”

“Yes Daddy, I love it!” my sister nearly screamed over her moans.

“What are you?” Brian asked her insistently. 

“I’m your little exhibitionist whore, Daddy.” she cried.

“Good, then cum. Cum for me.”

The screaming cry that came out of my sister was completely unintelligible, but very clearly a powerful orgasm. Brian soon followed, grunting as he shot a load in my sister. As they came down off their high and both lay on the bed, their gaze turned to myself and Lexi, putting on a show for them now as I rubbed her through the thin fabric of her swimsuit. Unfortunately things were not going as well over on our end. Lexi was more than capable of having multiple consecutive orgasms, but if we waited too long in between it was like something shut down and it became much much harder. The orgasm in the car had been her first and what we were trying now was just too long afterward, but not long enough for a full reset. 

After what seemed like an eternity, but was likely only a couple minutes, Lexi gave out a frustrated sign and asked me to stop. I removed my hand and she closed her legs. Somehow, this was the most embarrassing part of this experience so far. My sister seemed genuinely concerned when she asked “Everything okay hun?”

My girlfriend explained the situation to my sister, who simply nodded and listened. When Lexi was done, my sister asked Brian to untie her and then go fetch some water. The ropes were far easier to dof than to don, and soon Ella was free and beckoned us over to the bed, while her husband left to make some ice water. “You know, every woman is different, and this is not a failure on either of your parts” she said, clearly seeing the embarrassment on both our faces. “But, I think I have something that might be able to push past the issue. Not quite the nuclear option, but damn close.” She paused to take a drink of cold water that Brian brought to her. “Still horny, Lex?” she asked.

“Yes.”

“Still need to cum?”

“Oh my god yes.”

She addressed both of us. “Are you comfortable if I help a little bit?” We looked at each other and nodded. My sister smiled, and fetched something from a suitcase. I recognized what she grabbed, a Hitachi magic wand. I had seen them before, but never in person. I think Lexi had as well, because her eyes went wide. “This little baby might have enough juice to force the issue, even if there is a bit of a block” my sister exclaimed happily. “I’ll give it a go, but you better watch closely Davy, cause this is your only freebie and the next one’s on you.”

My sister plugged in the hitachi and stretched a condom over the head of the massager. She climbed back into bed and positioned herself in between the legs of my still trussed-up girlfriend. Turning on the massager, she placed directly onto the knot that was pressing into the crotch of Lexi’s bathing suit. Lexi moaned and arched back into my arms. It was incredible, and clearly making an impact as, before long, she was shaking in my arms. My sister had her devilish grin again as she rubbed the massager in circles around the rope knot. Within a minute Lexi’s pitch had changed and it was clear she was getting close. My sister took the opportunity to press the massager hard into the knot causing Lexi to scream, lift her hips off the bed as she arched, and may well have squirted all over my sister, save for the bathing suit. 

Lexi fell back to the bed, panting when my sister turned off the massager. My sister and brother-in-law went to fetch us water while Lexi recovered. I began to untie her and, despite heavy breathing, she turned to kiss me furiously. Ella and Brian walked back in to see us making out and my sister giggled. “Horny teens… hold your horses kiddos, the boys still need to get tied up.”

I finished untying Lexi, we both gulped down water and caught our breath. All the while, Brian was discussing more about rope safety and other things that could be done with the karada. He showed us the safety shears that he had ready in case rope needed to be cut quickly, and gave us an extra pair that he and my sister had on hand. Finally, it seemed like everyone had recovered, my sister hopped off the bed and started selecting some rope. “Okay boys, your turn!” She said excitedly. 

Brian and I took positions where the ladies had been prior and they began karadas on us. The first steps were repeats of what had been done earlier, so Lexi did not need much additional instruction. However, when it came to the crotch, my sister explained how to do things differently for the male anatomy. “Of course we need to route the two ropes around either side of the cock, even over their underwear” Ella commented on her actions as she tied her redressed husband. “That said, you can still add a little something to stimulate a guy. Ever heard of the perineum?” she asked my girlfriend. Lexi simply shook her head. “Basically, the perineum lies between the base of the cock and the asshole. Putting pressure on it can stimulate a guy similar to putting pressure on the prostate if you ever get him to try some ass-play” she winked at us as she began to tie a knot in the rope which would put some pressure on Brian’s perineum. 

Lexi followed suit, tying a knot for me and moving on to the rest of the harness. As she tightened the ropes, the knot dug in and while it was not immediately pleasurable, it did not feel bad either. As Lexi and Ella finished up the main section of the harness, my sister got another of her devious looks. “Okay Lex, for the next part we are not going to be copying what the boys did to us, we are going to do a different tie for their arms… I have an idea…”. The girls proceeded to tie Brian and I such that our arms were crossed in front of us, each hand reaching to the opposite shoulder.  Brian wore a sly smile almost as soon as Ella started, so I assume that he knew exactly what she was doing. Lexi followed her directions perfectly and mimicked the tie. When all was said and done, my sister beckoned Lexi over and whispered something in her ear that made her eyes go wide and a big smile spread over her face. 

Ella handed over a leash and the hitachi to Lexi, who stalked back over to me with a very mischievous smile. I knew her well enough to know the look meant she knew exactly what she wanted, and that I should not argue. So I just stood there quietly as she attached the leash to a section of rope near my neck and began leading me out of the room. As we exited, I heard my sister call out “Have fun you two! When you are done we will debrief and have dinner” before shutting the door to my parents bedroom behind us. Lexi led me back to my own bedroom and helped me onto my bed, laying flat on my back and found a blindfold I actually used to help me sleep. She put it over my eyes, casting me into darkness and leaned over to whisper in my ear. 

“I love the way you look right now,” she said in a low tone. “Next time I am going to tie up your legs too and leave you truly helpless. For now, you are going to lay there and be my toy and I am going to ride you and get off as many times as I want…” 

With that she started working my boxer briefs down. Not the easiest task, considering they were underneath the tightly tied ropes, but eventually she got them down just enough to free my cock. Between being tied up and what she had just told me, I was almost painfully hard and more than happy to be free from my underwear. I heard Lexi open our bottle of lube, felt the cold liquid poor down my cock, and shivered in need as she stroked my cock to spread it around. She climbed on the bed and mounted me like some saddle, though she did not immediately start to ride me. Instead I heard a switch flip and the buzzing sound of the hitachi. Lexi pressed the device to her clit, letting out a moan as the vibrations shot through her. I too could feel the hitachi as the vibrations radiated through her on it felt almost as though her pussy itself was a vibrator. At the same time I felt it all through my pelvis and all of these sensations were so great that I could not keep myself from bucking up into her. She quickly took hold of the leash again and gave a firm tug, wordlessly telling me that she was currently in charge and I should stay still. 

I did my best to comply as, for what seemed like both hours and minutes, Lexi rode my cock hard, all while continuing to hold the hitachi to her clit. Her first orgasm washed over her and I felt her tighten up and scream, though she did not even slow down as she moved up and down on my cock. I would soon follow suit, bucking my hips in spite of my attempts to restraint myself, as I unloaded into her. She kept riding, and my cock was so sensitive after my orgasm that the intense pleasure started to border on pain and I writhed under Lexi. She responded by grabbing me by the chest portion of my harness and pulling me into a passionate kiss as she came once again, moaning into my mouth. This continued until each of us had had at least one more orgasm, to be honest it was such a blur I could not think straight, and she dismounted to fall beside me in the bed. 

After catching our breath, Lexi untied me, we showered and cleaned up. We soon went to the kitchen where Ella and Brian were hard at work on dinner for the four of us. As they worked, they answered Lexi and I’s questions and my sister even offered us a book on shibari she had so that we could build off what we had learned. The rest of the evening was casual, simply dinner and a movie but at the end of the evening, as I was seeing my girlfriend to her car, my sister promised ‘lesson 2’ would be next weekend. Lexi kissed me good night and said we should ‘practice’ some this week, before we had our next lesson, an offer I readily accepted.