Niki stood in front of her mirror, her back turned towards the door as she tried to finish getting changed after her workout. She has just stepped out of her sweaty gym clothes and is now standing completely naked, reaching for a baggy sweater to put on. As she bent over to grab the sweater from the basket, her muscular rear flexed and her shorts dropped to the floor. She was unaware of the fact that the door had been slightly open and now stood there with her round, firm ass exposed and her large tits sway slightly as she moved.

As she reached to grab her sweater, her body blocked the sight of the open door. Suddenly feeling a bit off, she turned around just in time to see her stepbrother Justus standing there naked and jerking off. She blushed deeply and gave him a disapproving glare before turning back around and putting on her sweater. "Justus," she started, speaking with her straightforward tone as she kept one hand on the door handle, ready to push it open should she need to leave quickly. "You shouldn't be doing that; you can get in trouble."

Her face flushed as she said it, a mix of embarrassment and anger. She felt dirty just for having seen him like that, but at the same time, a part of her felt weirdly aroused. It was definitely wrong and gross...but damn he looked good.

"Well," she started as she let go of the door handle and turned fully around to face him, "You should really learn some self-control then." Her voice was still blunt and honest; there was no hint of apology in it.

She took a step closer towards him, her nipples hardening beneath her sweater as she moved. "But if you're going to be doing that," she continued, a sly smile forming on her lips, "then at least let me join you." Without waiting for his answer, Niki climbed onto the bed and laid down next to him, facing him. Her body pressed against his naked skin, causing both of them to shiver slightly with arousal.

"So," she said, her voice lowering as she leaned in close enough that their lips were almost touching, "what do you want me to do?" She batted her eyelashes suggestively

Eagerly, she closed the distance between them and kissed him back passionately, her tongue darting out to duel with his. Her body arched into his as their lips moved against each other hungrily. She slid a hand up his chest, digging her nails lightly into the skin there, while the other hand reached between them and began massaging his cock through his cloths. He responded by grabbing one of her large breasts in his hand and roughly squeezing it, pinching at her nipple through her sweater.

They moved together on the bed, their mouths locked in a heated kiss as they began grinding against each other. Niki moaned into the kiss, arching further into him with every thrust of his hips against hers. "God," she breathed, breaking the kiss and looking into his eyes, her own glassy with desire.

Niki nodded eagerly and reached between them to grab his hard cock, guiding it towards her entrance. "Fuck yes," she breathed, gazing up at him as he slowly pushed inside of her. She arched her back again, crying out softly as he filled her completely. Her hand slid down over their stomachs to grasp his hip, pulling him closer still as they began moving together in rough, hungry motions. "Oh fuck," she groaned, her eyes slipping shut as the pleasure consumed her. "That feels so good." She bit her lip, tasting blood, and looked up at him again through hooded lids.

Niki growled his name, nails digging into his skin as she arched her back further, meeting each thrust with a thrust of her own, their hips slapping together in rhythm. Her breath came out in short gasps and moans as the pleasure built higher and higher inside her. "Fuck, Justus," she panted, eyes half-lidded with desire. "I'm close..." She thrust up into him one last time before crying out as her body tensed and shuddered beneath his, orgasm washing over her in waves of pure pleasure.

Her orgasm subsided but left her feeling incredibly satisfied and strangely connected to him. She looked up at Justus with a sated smile as he let out a groan and arched his back, his eyes squeezing shut and lips parting as he finally released inside of her. Niki wrapped one arm around his shoulders, holding him close as they lay there, panting heavily from the exertion.

After what seemed like an eternity, they both began to laugh, still breathless but unable to stop the amused chuckles from escaping their lips. "Well," Niki managed between giggles, "that was...surprisingly fun." She blushed and looked away briefly before adding, a touch more gruffly, "Though you could work on your aim next time we do this." A small smile tugged at her lips as she waited for his reply.

Niki giggled again and rolled her eyes playfully before responding with another genuine laugh. "Don't count on it," she said teasingly. "But if you're really that desperate..." She paused, a mischievous glint in her eye. "...I guess we could do it again sometime." Her voice softened slightly as she added, "But only if you promise to be nice this time." A small smile curved her lips upwards as she reached up and brushed a strand of hair out of his face.