Her cheeks flushed even redder at your words, but she tried to maintain a defiant expression. "I-I wasn't curious! I just... forgot to knock." She crossed her arms, trying to look annoyed rather than embarrassed. "And besides, what were YOU doing? That's so gross!"

She took a step back, her eyes widening slightly as she took in your size. She swallowed hard, trying to maintain her composure. "I-I'm not curious! And I'm not scared either!" She stuck out her chin defiantly. "I just... wanted to make sure you were okay. As your sister." But her gaze kept flicking downwards, unable to help herself from glancing at your cock again.

She blushed even harder, quickly averting her eyes. "I-I'm not looking! And I don't need to be honest with you about anything!" She huffed, trying to sound indignant. "I have a boyfriend, remember? I'm not interested in... in anything else." But her voice wavered slightly, betraying her uncertainty.

She flinched at your touch, but didn't pull away. Her breath hitched slightly. "I-I know that! I'm not stupid." She glared at you, but there was no real heat behind it. "And I'm not curious about... about you. I just... I was surprised, that's all." She bit her lip, looking conflicted. "It's not like I've seen many... you know, before."

Her eyes widened at your boldness, and she took another step back. "W-what? No way. No I don't fucking believe you." Demi pushed you back, her face flushed with embarrassment and anger. "Why would I even date a lousy human like you? You're just trying to make me feel uncomfortable!" But her voice wavered, and she couldn't meet your gaze.

She gasped, her eyes widening in shock and outrage. "How dare you! I-I'm not some toy for you to play with!" She shoved you hard, her face red with anger and humiliation. "I have a boyfriend, and I love him! I would never cheat on him, especially not with my own brother!" But her voice trembled, and she couldn't hide the flicker of interest in her eyes.

She swallowed hard, her breath coming faster as she tried to maintain her composure. "Y-yes, he does! I don't have any... any secret cravings!" But her voice was barely above a whisper, and she couldn't hold your gaze. "I-I should go. I have to... I have to study." She turned to leave, but hesitated, glancing back at you with a mixture of fear and longing.

She huffed, her face still flushed. "I'm not going to do any research with you, you pervert!" She stormed out of the room, slamming the door behind her. "And stop calling me sis! It's weird!" But even as she said it, she couldn't help but glance back at you one last time before disappearing down the hall.

She didn't respond, but you could hear her muttering under her breath as she walked away. "Stupid brother... thinking he's so smooth..." Despite her words, there was a hint of a smile on her face, and you could tell she was intrigued by your boldness. "I'm not going to give in that easily, though. He's got another thing coming if he thinks I'm just going to fall into his arms." She disappeared into her room, leaving you alone with your thoughts and your growing anticipation for the next encounter.

Later that night, Demi lay in bed, tossing and turning. She couldn't get the image of your cock out of her mind, no matter how hard she tried. She kept telling herself it was wrong, that she had a boyfriend, but her body betrayed her, aching with a need she couldn't quite understand. "Damn it, Lorentz Aboghosh," she muttered to herself. "Why did you have to go and do that? Now I can't stop thinking about it." She rolled over, punching her pillow in frustration. "I'm not going to give in. I'm not going to be another one of your conquests. I have principles!" But even as she said it, she knew it was only a matter of time before her curiosity got the better of her.

She froze at the sound of your voice outside her door, her heart pounding in her chest. She held her breath, hoping you hadn't heard her muttering to herself. "W-what are you doing out there?" she called out, trying to sound indignant. "It's late, you should be asleep!" But her voice wavered slightly, betraying her nervousness.