This idea popped into my head when I was reading another Sizzy fic and I just had to write it down. It's my first venture into M so I hope I did okay.

First love

Simon panted against Isabelle's neck where he could almost hear her blood rushing through her veins. But, surprisingly, he felt absolutely no desire to taste her blood again, not when she was pressed as tightly as possible against him and was still shaking in his arms. He lifted his head slowly, took a peak at Izzy's sweaty face and something in his chest tightened. Large, dark eyes stared back at him. Eyes that were shining with love and lust. For him.

His hands that were resting next to her face brushed gently over her cheekbones and tucked a damp strand of hair behind her ear. His thumb brushed against her earlobe and Izzy hissed softly. Simon jerked in her embrace, an apology ready on his lips when she turnt her head, flicked her tongue against the pad of his thumb and her whole body tightened around him. Simon watched how her teeth sank into her bottom lip, realisation dawned on him and he softly pulled on her lip to free it again. Slowly, Simon lowered his mouth to Isabelle's and was rewarded with a moan that hit him straight in his stomach. Her leg raised itself involuntarily, wrapped around Simon's slim hip and he felt his whole body harden again. Hot tingles ran over him, pooling deep inside of him and making him want more – again.

"Iz," he whispered against her swollen lips. "Do you have another -?" He stopped, somehow embarrassed to use the word. But she knew what he wanted to ask, of course she knew. Her hand had already reached out to his nightstand and Simon felt a surge of love for her. Isabelle Lightwood had somehow managed to steal his heart and apart from Clary she knew him better than anyone else. Hell, she now knew him better than even Clary. The intimacy they had just shared, their first lovemaking, his first time; Isabelle was now familiar with all of him. His thoughts, his hopes, his fears, his body. A body that she had practically worshipped with her hands, her lips, her tongue and also her teeth before it happened.

A warm hand on his cheek roused him from his thoughts, "Where did you go?" He shook his head as if to clear it. "Just thinking about what just happened." Isabelle's eyes sparkled and Simon was stunned to see that they had changed colour. Her eyes that were usually almost black had lightened. There was still a dark ring but the rest was suddenly a warm chocolate brown. He ran his index finger over her brow, dropped a lingering kiss to it before he looked into her expressive eyes again. "How your touch caressed me and how it felt like you were worshipping my whole body." Isabelle's other hand, the one that was still resting on his back, moved upwards, lovingly stroking his spine, his shoulder blades and his jaw before both of her hands were cupping his face. "That's because I was worshipping your body." Simon's temperature rose when her words were also accompanied with a slight change of her hips which made him more aware that he was still resting comfortably inside of Isabelle. He was barely able to hold back a groan and he stared at Izzy intensely, "G- Deus! I love you." A beautiful smile appeared on her still swollen lips before she cheekily replied, "I know." This time Simon couldn't hold back his groan and he buried his face in her neck again to breathe in her scent, sunshine, sweat and something that was distinctively Isabelle. "I really shouldn't have told you of this fantasy," he grumbled against her skin. He felt her laugh vibrating against his chest, "I'm glad you did. And I love you too, Simon." His heart which usually lay dead in his chest, jumped slightly at her words. Just liked it always jumped when she so freely admitted her feelings for him. The first time Isabelle had said 'I love you' to him, Simon thought that his heart would jump right out of his chest into her hands where it belonged. He didn't care how cheesy it sounded, but his heart was hers. He felt her moist lips run over his cheek and another burning question formed in his mind, "Did you like it? Did I do okay?" She smiled against his skin before she looked him in the eyes, "Yes." And this simple word was enough for him. He knew that Izzy wouldn't lie to him, just like he knew that she hadn't come but didn't mind because with a little practice the next times were going to be even better – for the both of them.

Isabelle shifted underneath him again, making Simon concentrate on the parts that were still connecting them. His hipbones were slightly pressing into her soft flesh whereas her rising and falling chest was brushing against his skin. Simon mustered up his courage, "Isabelle, do we have another condom?" "I thought you'd never ask." Her hand reached out to his nightstand, dug around in her purse before she retrieved another condom wrapper. Isabelle held it between them, looked at Simon expectantly and whimpered softly when he slipped out of her. His eyes widened, "Did I hurt you?" She brushed a hand over his jaw, "You didn't hurt me, but after having had you inside me, I feel a bit empty now." A blush rose over his cheeks at her words, but then a surge of confidence grabbed him. He had nothing to be embarrassed about and he wanted to please her. Simon finally left her embrace, feeling oddly cold after being surrounded by Isabelle for so long and then he stripped off the condom, wrapped it in a tissue and held out his hand for the new one. Izzy shook her head, "Let me do it." She pressed him down on his mattress, knelt beside Simon and carefully opened the wrapper. His whole body jerked when her slender hand wrapped around his erection, stroked him for a few moments and then sheathed him with the thin condom. Isabelle swung her long leg over his hip and positioned herself over him. Simon's skin felt like fire again, it prickled and burnt and his temperature rose up another notch when Izzy's hands softly pressed against his chest. She sank down on him, mutual groans escaping them both. Simon began to see stars when she adjusted her position until they were both comfortable. Then Isabelle gave him her most beautiful smile before saying, "I'll show you what to do so that we'll both come."

And she did exactly that.

Thanks for reading! Reviews are much appreciated.

In case you're wondering why they used condoms when Isabelle obviously cannot get pregnant, there are still sexually transmitted diseases – not that Izzy has one – and I wouldn't have felt comfortable writing a fan fiction without safe sex.