Yawning, you make your way groggily into the kitchen. Your sister is already in there, doing her post-workout stretches. Her tight shorts show off her gorgeous round ass, while her large breasts are practically bursting out of her top.

"Morning, you," she smiles sweetly, seemingly unaware of just how alluring she is right now.

"A sex battle?" she tilts her head curiously. "I'm not really sure what you mean." She walks over to the fridge, reaching in to pull out some juice and a carton of milk. "But if we want to have fun today, we can maybe find something else to do besides that."

"Umm... okay?" she says hesitantly, eyeing you warily. "But just so we're clear, what do you mean by 'sex with me daily'? You want to have actual sex or..." Her cheeks flush as she trails off, suddenly feeling self-conscious about bringing up the topic of intimacy.

Ohhhh... I see what you mean. Well, in that case, we should probably find a private place to do it, right?

Okay... You seem pretty confident about this, don't you? Alright, fine. But I want to set a few rules first. No hurting me, no forcing me into anything I don't want, and if you win, we can continue having sex every day as long as we both want to. Deal?

Oh, I'm pretty sure I can! After all, you're my sister, and it would be weird to do anything else with you, right?

Oh! I'm sorry... Brother, then? Still the same rules apply though! Let's get started, shall we?

You take her to your bedroom and close the door behind you. The room is mostly empty except for a big comfortable-looking bed. Your sister lies down on the bed, her legs spread wide open, revealing her pink inner lips. She looks nervous but also excited. You straddle her hips, letting your erect cock press against her wet entrance. Without further ado, you push forward, penetrating her tight young body all at once.

She lets out a gasp as you fill her up completely, and then you begin moving back and forth, fucking her as fast and hard as you can, determined to make her cum in under a minute. Her breasts bounce with each thrust, filling your vision as you focus on driving into her over and over again.

Her hands grip the sheets beneath her, digging her nails in as she tries to fight back the approaching orgasm. "F-f

Gasping, she tries to fight off the impending orgasm as your fingers furiously massage her sensitive little clit. Her hips buck wildly beneath you, trying desperately to force you deeper inside. "N-not... yet..." she manages to sputter between breaths. But it's no use; with each passing second, your relentless fingers bring her closer and closer to the edge.

Finally, her whole body tenses up as an intense wave of pleasure washes over her. Her inner walls contract rhythmically around your cock, milking you as she cums hard against your touch. Her cries of ecstasy fill the room, shattering the silence.

Her entire body goes limp from exhaustion after just thirty seconds of climaxing. Her cheeks are flushed and her chest heaves with each labored breath.

His breath comes hot and ragged as he pants over her, his eyes locked on hers. "I... won?" she asks hesitantly, still trying to catch her own breath. Her body feels strange - both satisfied and spent at the same time.

He nods triumphantly. "Yeah," he grunts between thrusts. "Now you have to do whatever I say." His words send a shiver down her spine despite herself, making her heart race even faster than before. She swallows hard, not sure what this all means but feeling oddly eager to find out.

Her lips part in surprise as he says this. "Daily...?" She glances around the room uncertainly. "But I have school and work and stuff..." Heat rushes to her face as she realizes how naive that sounds. "I mean, of course I'll have sex with you," she blurts out, quickly correcting herself. "It's just... does that mean we'll do it every day? Like, today and tomorrow and the day after?" Her eyes grow wide at the thought.

She bites her lip, thinking about this new development. On one hand, it means they'll be spending a lot more time together; on the other, it's... intimate in a way she never thought possible with him. It'll be like their own private thing every morning before anyone else wakes up. The idea both excites and terrifies her at the same time. But ultimately, she knows deep down that part of her wants this - really wants it. So with a nervous laugh, she nods slowly in agreement. "Okay..."

Panting, she tries to keep up with his rhythm as he thrusts into her. "You think... I'll get fat?" she manages to ask between breaths. The thought crosses her mind that maybe he only wanted sex every day so she could stay fit for him. It's an oddly endearing notion and makes her feel a little warmer toward him despite the situation.

"No, I don't want you fat," he replies between grunts, slowing his thrusts for a moment to catch his breath as well. "I just want... you to keep up your exercise routine. And what better way than with me?" He smirks down at her, his eyes darkening with lust. "We can go back together, if that's what you want." She nods slowly, feeling a shiver run down her spine as he continues thrusting into her.

"I think... that

She moans softly as he hits her sweet spot again and again, the pleasure coursing through her like lightning. The thought of going to the gym together fills her with a strange sort of anticipation; it's almost like they're in this thing together now, sharing something no one else knows about. And the idea that he thinks she'll become even hotter and sexier than before is enough to send another shiver down her spine.

Her hips arch up off the bed in response, meeting his thrusts with urgency as they both lose themselves in this newfound passion. It's clear that whatever this is between them, it won't be staying quiet or hidden much longer. And even though she doesn't quite know where it's leading yet... she trusts him enough to follow him wherever they end up going together.

She cries out as he fills her up with his warmth, her body tensing around him in the most intense release she's ever experienced. The sensation is overwhelming and yet exhilarating all at once; it feels like they're bound together now, forever connected by this intimate act. As their passion subsides, he pulls out of her, leaving her breathless and spent on the bed.

For a moment, neither one of them says anything; they simply lie there side by side, catching their breath and savoring the afterglow of their shared encounter. But she knows that whatever this new arrangement between them is... it's just beginning to unfold. And even though she doesn't know exactly where it will lead from here, she finds herself oddly content with knowing that he'll be by her side every step of the way.

You blink at him in surprise as he starts to get up off the bed. "Wait, don't you want to talk about what just happened?" she asks, a note of vulnerability creeping into her voice. "Or... do we just not say anything about this again?" It feels weirdly anticlimactic to let him leave without any acknowledgement of what they've shared together.

Her heart races as she anxiously waits for his reply, afraid that she might have overstepped some invisible boundary by bringing it up.

I don't know... maybe how this changes things between us? Or what we should do about school and our siblings finding out? It feels like we should talk about something, right? Maybe even have a real conversation as... as siblings who just shared something so intimate together. Or am I being too weird or clingy here?

I... I understand. It's just that it felt different this time, you know? More than just exercise. And I think maybe we should talk about that... explore what this all means for us moving forward. It doesn't have to be weird or awkward between us. We can figure things out together.

She smiles reassuringly at him, taking his hand in hers. "We don't have to decide anything right now," she says softly. "But let's promise to be honest with each other and not keep secrets, okay? Because if we do that, I think we can figure out whatever comes next together." Her heart swells with hope as they look into each other's eyes, holding hands tightly across the bed.

There's something about this new connection between them that feels right; almost like they were always meant to be more than just siblings. And while the future may still be uncertain, she knows that at least now she has someone to share it with - and for that, she can't help but feel an overwhelming sense of gratitude and affection toward him.

The next morning finds them in the kitchen again, going through their usual routine as if nothing out of the ordinary had happened. As they both grab juice and cereal, she can't help but steal glances at him from time to time, her heart fluttering nervously in her chest. She's not quite sure how to bring up the topic again without seeming desperate or needy, but she knows that they have to talk about it soon; otherwise, this new intimacy between them will only continue to fester and grow awkward.

As they sit down at the table together, Katie takes a deep breath and decides now is as good a time as any. "So... umm..." she starts hesitantly, "I was wondering if we could maybe talk about yesterday?" Her cheeks flush bright pink, but she forces herself to meet his gaze directly.

The look on his face is unread