This is a mature One Shot fanfic. I wrote this last year and forgot about it until now. I can't even remember when i thought about this story. It doesn't really matter anyway... they're a good pairing!

Disclaimer: I obviously own nothing :(

Isabelle was in her room when Simon knocked on the door. Hesitantly he asked: "Can I come in?" He knew that he had done something to upset her, but he just didn't know what. They were having a really steamy make out session on the couch downstairs when isabelle stopped them abruptly. Before he knew it, she ran up to her bedroom and locked herself in.

She yelled at him: "Go away simon." For some reason, he had done something to make her mad. It always seems to be the guy's fault doesn't it, he thought. "Babe, please just open the door… If you don't then I'll break it down. I've got vampire super strength and all." He joked. Just as he was about to give up and turn away, she opened the door. Isabelle glared at him and said: "Stupid ex-mundane blood sucker." Hearing her say that stung simon. She's never called him a blood sucker. He always thought ever since Simon and Clary came into their world with the Lightwoods and Jace that Isabelle had become less snobbish towards Mundanes and downworlders. Obviously, she had grown more mature since that night in Pandemonium, because here he was a vampire geek who still played Dungeons and dragons dating the most beautiful and strongest shadowhunter he knew for the past two months.

"Izzy please. Tell me what I did wrong so that I can fix it."

"It's just…" Isabelle was never the one to refrain from saying what she felt. In fact, she was very blunt when it came to honesty, but right now she seemed to be hesitating with her boyfriend.

Simon approached her slowly and said in a soft voice: "What.. Tell me." He took her hands into his and looked into her eyes. Simon had never been this happy in a relationship before and he thought everything was going great. This wasn't the first time Isabelle would react this way after they were kissing for a long time. Maybe it was his kissing.. oh no had it been his fangs? Had he hurt her? He'd always been so careful. His hand shot straight to his mouth. "Was it my fangs? They disgust you don't they..." Poor simon… but how can he be so clueless she thought.

"No of course not. Don't be silly. You're anything but disgusting. The fangs don't scare me either. Shadowhunter, remember?"

"Oh thanks izzy. You really know how to boost up a vampire's moral. So is it the kissing? Is that it? I'm a bad kisser. Aren't I?"

She burst into laughter when he said that. She knew it wasn't that funny, but she couldn't help herself. Here her boyfriend is worrying about his kissing upsetting her when in reality she is annoyed that she isn't getting anything more than kissing.

He gently squeezed her hands impatiently.

Then she finally said: "I'm sorry. There's nothing wrong with your kissing. I love your lips simon. I wouldn't be dating you if I didn't." This still hadn't relieved simon. He was feeling even more nervous now.

"It's just that's the problem. All we do is kiss. You never try to touch me…" She gasped: "Is it.. are you a virgin?" He looked at her in shock. She wants more? That's what this is all about? He didn't feel that his face flushed when he said slowly: "Umm no. I've done it before but it was really quick and awkward." She interrupted him: "Clary?"

"What? No way! No. It was just some girl at a party. I thought I was never going to get another chance. It was stupid. I didn't know you felt this way. Of course I want you. I want to be with you so badly, but I'm scared to touch you. What if I hurt you? I've never been with a girl as a vampire. I might lose control and bite you. I couldn't bear hurting you."

She held his face and kissed him forcefully. "You're so silly simon. You're not going to hurt me. I know it. Besides... I can heal really easily." Then she whispered into his ear: "Also, I want you to bite me." Isabelle took his hand and pushed simon onto the bed. She climbed on top of him which is just how she likes it. Simon had no time to react. The first thing he said was: "But what about protection?" For an intelligent guy, simon can be dumb sometimes. "Babe. You're a vampire. You're sterile."

"Oh yeah." He pulled her down and kissed her. He sucked on her lower lip and kicked off his shoes. His hands gently moved up and down her back while hers were on his chest. He moved his hands to her ass and squeezed it. She moaned with pleasure. This was a good sign. He thought. He'd always imagined what Isabelle would be like in bed. So far from what he understood she was the naughty dominating type. So he spanked her ass hard enough to make her collapse from surprise and he flipped her so that he was on top. She moaned: "Mmm sim-." He devoured her lips hungrily. He slipped his hands under her white top and hesitated whether or not to take it off. Isabelle sensing his hesitation slid down lower so that his hands were on top of her bra. He smiled and raised himself from her and took off her top. His lips parted as he stared at her chest. She was wearing a blue lacy bra that pushed up her breasts in a way that granted simon a pleasurable view. She smiled and pulled him down to kiss him again. He made circular motions on her back with his hand and teased her every few seconds coming close to the clasp of her bra but not really unhooking it. She wrapped her legs around him tightly as he slipped his hand on her right breast right under the bra. She gasped. He remembered that their body temperatures are very different what with him being a vampire. He pulled out his hand instantly and said: "I'm sorry. I must feel so cold to you."

She rolled her eyes and sat up so she removed her bra with one swift motion. Simon nervously looked at her beautifully rounded breasts and made a growling sound as she took both his hands and placed them on her breasts. He'd never thought breasts could be that soft.

"They're so soft.."

She moaned as he continued moving her breasts in circular motions. Gasping and harder every time. He attacked the left one with his mouth. He growled as he licked and sucked her nipple hard. Isabelle was moaning so loudly. She couldn't believe it. She had thought that she would need to instruct simon on what to do, but he seemed to know exactly what she wanted and the little vampire even had the balls to tease her. She let his mouth suck on her nipples, while she moved her hands to take off the belt from his jeans. Simon ran his hands up and down isabelle's body. He had never been more aroused. Still not breaking from sucking on her breast, because he had never tasted anything more delicious, he unzipped her pants. He hadn't noticed that isabelle had been panting until she tried to speak. "That's not fair." The only piece of clothing isabelle was wearing was the matching sexy blue lacey panties.

Simon gave her the sexiest look and grinned at her. "What's not fair?"

She pointed out: "I'm completely naked and you've still got your clothes on."

Simon gazed at her beautiful naked body under him and said: "Oh. I didn't think I had a body worth seeing. All you had to do was ask." He seductively pulled off his t-shirt and said: "See anything you like?" She stared at his bare chest and really noticed how much his body had changed. He was no longer that skinny stubborn mundane boy. Even though he was very pale looking, he had this strong healthy glow in him. He even had grown into having these kind of sexy pecks. She pulled him on top of her and both of them felt an arousing chill pass over them. It must be simon's cold body and her heated skin, but they both felt so good just by touching their bare bodies. Simon had started to kiss isabelle again when she whispered: "bite me!" Simon stared at her in shock. "What?"

"You heard me… I know you want to. Trust me. I want you to."

"No isabelle. I can't. I won't be able to stop." Despite saying this, he had been already feeling hungry since they got into the bed. He wouldn't bite her though. He couldn't.

"I know you can. I know you're hungry. I can tell."

He looked at her soft neck and thought about the taste of her blood. He knew it would taste so much sweeter than the animal blood. He leaned forward. "Push me off when you start to feel weak." Isabelle nodded and closed her eyes. Simon hesitated and said: "You know you don't have to do this. I don't want to hurt you. I don't know what I'd do if.." Isabelle held simon's face with both palms and reassured him : "I promise as soon as i feel any discomfort, I'll throw you out of the bed." He smiled and kissed her lips. He put his hands back to her breasts and squeezed them as he trailed kisses down her neck and shoulder. Finally he bit as gently as he could into her neck. Isabelle gasped and massaged simon's back as to assure him that she was fine. Her blood poured into his mouth and he felt like he was in ecstacy. Nothing in the world could compare to the taste of isabelle's blood. He let go and licked the two small bite marks on her neck.

Simon stopped and took a moment just to look at her smiling eyes before he said: "I love you Isabelle." Then he leaned down and crushed her lips with his.

Yeah i know i didn't really give isabelle a chance to react. Im sorry! Simon is such a sweety in my opinion. He cares and loves Isabelle so deeply. I just didn't want to continue this because then i'd have to write how isabelle is confused about her feelings and bla bla bla... I'm satisfied with this ending. I don't think i'd change it. I'll leave it to your imagination how the story plays out! Thank you so much for reading =)