Obey your master, you sister slut slave!

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Alan would have liked to stay in the living room and play with all the naked women sitting around him. It seemed like a real breakthrough evening and he wanted to take advantage of the increasingly permissive attitude to shred more of Susan's boundaries. He especially wanted to get her more used to committing sexual acts in front of the others, and to having two women service him at once. But he realized that he had to take care of Katherine's feelings first.

He took his sister to her room so they could privately discuss Amy's new official girlfriend status. He put on his T-shirt and shorts, thinking that would help create the right mood for a serious discussion.

However, she didn't bother dressing. She collapsed onto her bed naked, in a very sour and frustrated mood.

She started crying even before he could talk. She complained through her tears, "I thought I was number one in your heart! I want to be your number one fuck toy! Why won't you let me? Am I not sexy enough? Are my tits not big enough? Even though my tits aren't the biggest, I'm still your sister and your fuck toy, and you should love me! Including carnally!"

"I do love you! It's not that! It's just that I'm spread thin between all the beautiful and eager-"

She didn't give him a chance to finish. They sat side by side on her bed, but she impulsively got up and literally pinned him to the bed, shoving her pussy into his face in a frustrated attempt to get him to forget Amy.

"I'm a great fuck! Aren't I? Don't you like to slide your big baby-maker into my hot hole? Don't you want to fuck me?" She cried even more intently while trying to sexily smother him with her pussy.

He was forced to push her off, frustrating her even more. He didn't want to do anything sexual with her when she was crying and angry like this. He held her for a while and caressed her until her tears came to an end.

Then he tried to talk to her calmly. He told her as he wiped away her tears, "You know I love you more than Amy, don't you? I hate to say that kind of stuff 'cos it always hurts someone's feelings to compare people like that, but you're my sister and, as great as she is, she's not. I love YOU about as much as it's possible to love someone. It's like you're a part of me!"

Katherine nodded weakly, her eyes still red. Her tears were still rolling down her cheeks, falling into her lap.

She said, "I know. I feel that way too. That's why I love being your fuck toy. But still, I have a hard time believing everything you're saying, especially the part that you love me more than Amy. She may not be your real sister, but she's close enough!"

"That's true. And I feel weird even trying to make comparisons like that, because it's not fair. But you have a very special place in my heart! Very, very special!"

She wailed, "Then make me your official girlfriend!"

Alan's heart nearly broke at the sight of her crying. Her wide, innocent eyes could look as sad as a forlorn puppy dog. He felt swayed by her heartfelt emotion but knew he couldn't have her as his official girlfriend, so he kept his resolve.

"We can do anything we want in private, but in private only. There are just certain things society won't let us do. You know that."

"I know. But fuck what other people think! True love conquers all. Fuck society!" She sniffed as a few new tears rolled down her face.

He shook his head no. "I wish! But you know we can't do that. For one thing, you have to realize that it's completely impossible for a brother and sister to be public about going out together romantically, even if we ARE both adopted from different families. I need a public girlfriend. My friends have been increasingly teasing me about not having one. It's more than just a little bit ironic that they still think I'm a virgin, but they do. Having Amy as a girlfriend will also protect her from the constant stream of boys who are only interested in getting a fuck from one of the school's most desirable girls. She's so clueless that she needs a lot of protection."

He continued, "And lately, more and more girls have been trying to go out with me. Honestly, some of the most beautiful girls in school have asked me out just in the last week. Of course I turned them down. But what if something strikes a perfect chord and I'm asked out by a girl who sweeps me away and makes me feel like I used to feel with Christine? Do you want me to be available like that, where anything can happen?"

She ground her teeth, fiercely possessive. "No! Of course not."

His line of reasoning was working. She was far more worried about someone else like Christine than she was about Amy. In particular, she was still very worried that Christine might change her mind about Alan and pursue him seriously. His "non-romantic" dates with Christine made her more jealous than all the sex he'd had with all his other women combined.

Alan saw her jealous reaction and tried to work with that to help convince her that Amy's new status was for the best for everyone. "Well then, look. I love Aims in a protective way like I'd feel towards a younger sister, and I love her in a physical way too. I like spending time with her, but I don't feel a deep, soul-to-soul connection the same way I do with you. I'm looking for a strong, independent woman who's smart and challenges me with strong, intelligent opinions. Amy's too passive and accepting to be like that. Christine is like what I want, but she lost her chance. I'm soooo over her."

"Are you really over her?" she asked while sniffling.

"Of course," Alan said, though he wasn't too sure about it himself. "You're like her in a lot of ways, you know, especially if you'd pay more attention to doing well in school. You're so smart, but you don't really apply yourself. The point is, I love talking to you and being with you, in addition to having sex with you. You're much more than just a sister. You're the one that I want, forever."

Her heart soared upon hearing that, and her face even burst into a smile.

He let that sink in, then continued, "Aims would make a good ... mistress. Maybe when we're done with high school, the three of us can go to college in the same town. We could change our last names, and you and I could be boyfriend and girlfriend, openly. Amy could be my mistress. OUR mistress. I think she'd accept that, and maybe even welcome it. I'll make sure to steer her in that direction. In fact, I won't even have to try. She'll love it."

"That sounds really good." Katherine momentarily daydreamed of being her brother's wife, with Amy as their mutual mistress. She imagined herself with a big pregnant belly and lots of little children running around. Most of them were birthed by her, but a few were birthed by Amy. She smiled wistfully as she unconsciously rubbed her stomach.

But then she returned to the current situation. "I'm still upset, but I guess I can live with it. I was so afraid you'd forget all about me when you said you'd go out with her." She felt her panic flooding back. "For one thing, you and Amy are one grade ahead of me. You'll be in another town for a whole year without me!"

"Don't worry; we'll work something out. Sis, we're rich enough. We can do whatever we want." He kissed her lightly on the cheek.

She forced another smile, but was still pensive.

He added, "I'll tell you what. I'll make you a deal. For every time I fuck Amy, I'll fuck you at least twice. How does that sound?"

"Now you're talking!" She threw her arms around him and they kissed some more.

After several more minutes of making out, they took a break to catch their breath.

Katherine took the chance to say, "You know, speaking of being a mistress, I've taken to referring to you as 'master' when I'm with Aunt Suzy. It turns me on so much to imagine that I'm literally your slave, your sex slave, forced to obey your every whim. I know how much it turns you on too. I suspect the idea of being your sex slave even turns Aunt Suzy on, but she's won't admit it to herself and doesn't use that word. Yet! She's too proud. And of course Mom is a total goner, completely enthralled by your cock. She worships it and lives to serve you, just like I do. Anyway, the point is, I think Amy will love being your mistress. I know she will. It fits her personality so well. Since you've discovered your sexual side, women just can't say no to you. And you're such a good master. So kind and fair."

Alan was blown away by that, and more than a little aroused too. "Come on. I'm not your master; I'm your brother!"

"I know! Isn't it great? You're my brother AND my master! Two great tastes that go great together! Though funnily enough, both taste like cum." She giggled with pure delight while licking her lips.

He loved what she was saying, but he was also in denial about it. It was fun as a fantasy, though quite daunting in reality. "Sis, let's talk about this later, okay? I've had enough emotional upheavals for one evening. I'm happy with you just as my sister."

"Okay, Master. Whatever you say. Your sister-slave happily obeys her well-hung fuck-monster brother. I'm going to make you forget all about Amy by being the best, tightest, most talented and obedient fuck toy you've ever had. Let your fuck toy make you feel good! She wants you to fuck her right now!" She threw herself at him and held him again in a tight embrace.

"'Fuck toy'? 'Sister-slave'? Come on! I thought that was just sexy talk." He was disturbed, but also terribly aroused. He tried to hide his arousal by discretely shifting his erection, but the way her naked body writhed against his own made that very difficult.

She looked at him intently. "No. How many times do I have to tell you? Your fuck toy takes her responsibilities very seriously. And she needs to make you feel so good that you pass out with joy. Every day!"

"But what about my desire for a strong, independent, intelligent woman?"

"No prob, Big Brother. I'll be your strong, independent, intelligent fuck toy! Okay, scratch the independent part. That's good for other parts of my life, but when it comes to you, I'm an obedient cum slave with no free will except for an 'uppity' desire to be fucked! But two out of three ain't bad, right?" She giggled.

He just stared at her like she'd grown an extra head.

She continued more intently, "I know you as well as anyone, and I know what you like. Strong and intelligent is good, and I can do that too, but deep down you want a SLAVE. Don't you? Who doesn't? What kind of teenage boy doesn't secretly want to turn their sexy sister into a sex slave, but you get to actually do it! And the beautiful thing is, I WANT to be your slave. Isn't it wonderful how it works out?"

Alan was very surprised at all this, and he wanted time to discuss it further. She was right; the idea was a big turn-on for him and he couldn't deny that. But the responsible part of him was also concerned. However, he had no chance to speak.

She was already holding him in an embrace, but then she pushed him back down onto the bed and started to ravish him.

As she nearly tore off his shirt, she said, "If you're going to fuck me twice for every time you fuck Amy, you'd better get a head start right now! I think the way you were fingering her a few minutes ago counts as a fuck." With a quick tug, she brought his shorts down past his feet and then threw them across the room. Then she lay on top of him, grabbed his erect penis, and tried to put it in her pussy.

"Does not!" he happily protested as he tried to fight her off.

"Does too!"

"Does not!"

"Does too!" She was beginning to gain the upper hand in their struggle. Since the consequences of his losing were hardly a bad thing, he wasn't trying very hard to win.

Alan still wanted to keep his vow to not fuck at home, and he was still worried about getting caught. He'd already forgotten that vow once, the morning before, and it would be all too easy to slip up again. His mother was sliding further into a sexual fog with every passing day, but he knew that she still thought that vaginal sex with her son was incest and a terrible sin. Having her see her children fuck each other would also freak her out in a big way, especially since both of them were already grounded for violating her rules. So he still struggled with his sister and fought to keep his dick out of her slit.

Finally, he yelled "Does not!" once more and grabbed her roughly by the hair to guide her head down over his erection.

Realizing what he wanted, she stopped struggling. She fell to her knees at the foot of the bed and assumed a cocksucking stance with her head bowed low. She thought that would help show how serious she was about her fuck-toy subservience, plus it just plain turned her on to be an obedient, incestuous cocksucker. "Is that all you want? Very well. I'm here to serve." She saluted him and said, "Number One Fuck Toy reporting for cocksucking duty, sir."

"Cut that out. You're too damn arousing!" He worried about cumming before she even got started, just from her arousing words.

"Master, forgive me for my enthusiasm. Your sex slave sister loves you. She loves you the most. Amy barely knows you, not like how I know you. I'll show HER! ... Now your fuck toy is going to prove her love and suck you off better than Amy could ever even imagine!" Then, with a parting shot in the silly verbal battle with her brother, she yelled "Does too!" and began sucking contentedly on his fat erection.

It's just like giving a pacifier to a baby, he thought as he listened to her happy slurps. But it's a hell of a lot more fun! Obey your master, you sister slut slave! You cum-slut fuck toy!

He was too shy to say that out loud, however, and immediately felt bad for calling his sister a "cum-slut" even in his own thoughts. What the hell am I thinking? That's wrong. I'll have to talk to her about this later. It's not healthy for our long-term relationship for her to act like this. I mean, I can still remember how I taught her to ride a bike, almost like it was yesterday. This is all very disturbing. The way I just snapped my fingers earlier and she came crawling to my dick like an eager... well, like a sex slave! It's wrong! I'm being corrupted by power. We really need to talk ... and discuss how we-

Suddenly he felt his climax coming on. But oh! Oh my God! So good! Too arousing! How can I fight it? Just like that, Sis! ... Right on! Yeah! He had to struggle and fight with his PC muscle so much that he lost his train of thought. Somehow he managed to hold off the orgasmic urge for a while.

They cuddled, kissed, and told each other loving sweet nothings during his strategic break. Then they repeated what was by now their standard procedure: she sucked him off until he was on the verge of cumming, and then they rested, giving his boner a "second wind."

The two of them had much to discuss, so they talked some more during these breaks. Admittedly, she had her fingers or even her mouth wrapped around his erection through much of the discussion. But she kept the stimulation to a minimum during his breaks. Sometimes she just liked to rest his hard-on inside her mouth so she could feel its presence there. At other times, she switched to a titfuck position and did all the work of sliding her breasts up and down on either side of his stiffness.

But while he was unwilling to actually fuck her in the house, he was very willing to play with her pussy. He toyed with her pussy lips and clit as much as she toyed with his dick and balls.

Alan didn't criticize her 'fuck toy sex slave' ideas, as he thought that might ruin her cocksucking mood and get her thinking about the Amy situation again. He figured THAT discussion could wait until sometime when he wasn't feeling so aroused. In reality, his heart just wasn't in it when it came to discouraging her submissive ways.

Instead, he soothed her emotions about Amy as best he could. He repeatedly complimented her and professed his love. But that only made her want to suck him off even more enthusiastically.

His orgasmic need had been slowly building with each close call, and eventually he realized that he'd reached the point where just about any further stimulation was going to send him over the edge. He really didn't want to cum, because he knew it had happened a remarkable number of times already since he'd woken that day. But he also didn't want to end their sexual fun, so he decided his best defense was a good offense.

His boner was trapped in Katherine's cleavage. She was slipping and sliding her big tits all over it while nibbling and licking at its tip. But then he suddenly pulled away.

She reached out for his hot pole. "Hey! Bring that thing back here!"

He replied, "Nope! Now, before you get upset, here's the deal. I'm right on the verge, and I don't want to cum. I've cum, like, seven or eight times already today. It's totally nuts! If I cum again, I think my dick is gonna cry for mercy. Just repeatedly getting right up to the edge is really awesome for me now. Besides, I want to return the favor. Let me go down on you."

Katherine complained, "What? No. That's all backwards. I'm your personal... excuse me, one of your personal cocksuckers. AND your Number One Fuck Toy, of course! I'm all about serving you!"

"I know, I know," he nodded. "But going down on you right now is what would make me really happy." Seeing that she was still reluctant, he added, "That's an order."

She smiled widely and spread her legs. "Well, if it's an order, I guess I can't say 'No.'"

He crawled up on her legs, reaching up to tickle her sides along the way. "Come on. You know you love it."

She grinned impishly. "Well, maybe a little bit."

They both chuckled at that.

Alan spent the next few minutes trying to bring Katherine to a big orgasm through his oral work. He still wasn't very good at it. His skills were pitiful in comparison to how her oral skill with him had advanced in recent weeks, but she had the advantage of much practice, as well as receiving tips from the other women in the house. Still, he had one very useful trick up his sleeve: orgasm denial. He told her that she was not allowed to cum until he gave her permission. Just the thought of him controlling her in that way got her boiling hot before he even started.

Then he got busy. Since she claimed to be so obedient to him, he also ordered her to tell him exactly what he was doing wrong, what she liked most, and to make suggestions on how he could improve his technique. Thanks to the resulting uncensored feedback, his licking skills improved by the minute. She was already extremely hot to trot, from her earlier activities, so he didn't need any extra generalized foreplay or teasing to work her up. He was able to focus instead on her slit and clit. Due to all his practice in "checking for bumps" with her and Amy, he was able to find her G-spot with ease, and any contact there really set her off.

It wasn't long before she was clenching her teeth and buttocks, struggling with all her might to obey his order and not cum. She waited and waited, but still, he didn't give permission. Eventually she begged and pleaded, but even so he still wouldn't relent.

He finally sensed that she was maximally aroused, about as much as she could get, so he yelled, "CUM! Cum, cum, cum for me!"

She most certainly did! Her screams echoed through the house. He kept at it until she was totally worn out.

Alan was tired too. He lay next to her with his penis in a flaccid state.

Thanks entirely to his self-control, the two of them had successfully refrained from fucking, even though they both very much wanted to do so as another way to reaffirm their mutual affection. She'd earlier given him the best and most prolonged combined blowjob and titfuck of their relationship, and now he'd returned the favor.

When she'd recovered enough to open her eyes, she looked at him and said, "Wow, Bro! That was amaaaaazing! You continue to impress. Remember my old diary entries, about how I fantasized about wanting to be your fuck toy?"

He wearily grunted, "Un-huh?"

"Well, the reality blows my best fantasies away! I have to admit that I enjoy when you go down on me, especially when it's an orgasm like the one you just gave me. But I love servicing your cock even more."

"Seriously?"

"Seriously. It's a submissive fuck-toy thing. I don't think you'd understand. For instance, I totally got off on that titfuck. A good ol' titfuck just seems like such a submissive thing to do, don't you think?"

Alan was wiped out, so he merely grunted an affirmative.

She cuddled up to him. "I love you, Brother. I really do. Please don't forget that, or even forget me altogether now that you have Amy."

"Are you kidding? I could never forget you. You're in my thoughts all the time. I love you too. So much!"

She threw her leg over his and seemingly tried to hug him to death. "Gaawwwd, why do you have to say things like that and then leave my pussy so horribly unfucked?!"

Despite the fact that he hadn't climaxed himself, Alan was left very sexually satisfied, in fact almost painfully so. He felt like his body had been squeezed through a wringer, thanks to the cumulative effect of so much sex in one day.

But he was also very aware that it was a Tuesday, and he realized that he likely hadn't seen or felt the last of his mother. He rested some more in his sister's room, cuddling with her, until he was ready to face more action in his own room from his double-decker mother.