A/N: Hey this is only my second fan fic so still be gentle with me! I have big plans for this story. It should be fairly long and have lots of twists and turns. Well the twists and turns you may or may not see coming, but a lot of things are going to be happening. Review a let me know what you think, and please don't be too mean . Thanks! And yes, of course this will be a Dasey. Anything else would just be a disgrace.

Disclaimer: I do not own Life With Derek.

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Chapter 1

Prologue: It is now the last couple weeks of Derek and Casey's senior year. Just to let you know what's been going on; Casey had dated Sam all the way up to the beginning of their senior year. Sam suddenly leaves town for no reason leaving Casey heartbroken and without any answers as to why he left. As for Derek, he had somewhat matured over the years. Instead of being "the player" when it came to the girls, he had settled down into a relationship with a girl named Jessica. They have now been dating steadily for the past two years. And so our story begins…

Derek POV

Jess was, as Derek thought when he first met her, the epitome of perfection. She was skinny, but not like starve yourself skinny, more of a healthy, eat- what-you-want-and-visit-the-gym-regularly skinny. She had long blond hair that flowed around her perfectly tanned face bringing out the color of her beautiful green eyes.

Derek was in love, or so he thought. They had had many wonderful times together. In fact she was Derek's first. He had to love her, right, if he was willing to give her his virginity?

All of this was running through Derek's head as he was getting dressed for Jessica and his two year anniversary date.

Still, there was something nagging away at Derek. Over the past few months things had begun to change between Jessica and him. He felt it and wondered if she did too. Although, he could never quite put a finger on what it was that was making their relationship change, making it feel much harder all of a sudden. He had a gut feeling that it was his fault, but he still couldn't figure out what it was.

Little did he know that tonight, Jess was about to answer all his burning questions for him.

Sitting in Derek's truck outside Jessica's house later that night after their date.

Derek was about to exit the truck when Jess stopped him by grabbing his arm.

"Derek, we really need to talk."

"Ok?" he replied. He could hear the concern in her voice.

"Derek," she started, "what's happened to us?"

She stopped allowing him time to answer, but Derek couldn't seem to find anything to say. Finally he managed to get out, "I don't know."

Her voice was now a little shaky, "We have been so great together, but these past months seem as if we're now just going through the motions. Do you not feel the same way?"

Derek couldn't lie. He softly said, "Yeah."

There was now a definite quiver in her voice now, "You say you don't know what it is that has made this relationship start to slowly crumble, but I do. It's you, Derek. You."

Derek's fears were now confirmed. It was his fault. But what did he do? He still needed answers, answers that apparently she could give him. So he let her continue, "I don't want to sound mean because I know you didn't mean for this to happen, but you do seem a little oblivious to it all."

Now Derek was really confused, "I don't have a clue as to what you are talking about, Jess."

"Casey, Derek. I'm talking about Casey."

"What about her?"

"You've been watching her heart slowly break with what happened with Sam and from seeing the way you look at her, the way I used to think you looked at me, I can tell a part of your heart is also slowly breaking."

Was he so oblivious to his feelings that he couldn't tell that his heart had indeed been aching over what was happening to Casey? He knew Jess was right, but for some reason he felt that he needed to deny it.

"She's my sister though, that's the only reason. I don't like seeing my sister being hurt," he said rather unconvincingly.

"Derek we both know that's not why. Just stop denying it. You have feelings for her, and not in a brotherly way. Besides she's just your step-sister. There's no blood relation, so there's no reason to feel ashamed."

Derek didn't know what to say. Jess was right. It was that simple. Slowly over the past months he had started to feel different around Casey. He noticed more things about her. He liked the soft features of her face, she didn't have the striking beauty like Jess, but it was a special kind of beauty. A kind that words couldn't describe.

Why did I not know this? Derek asked himself. Why have I been totally ignorant of my feelings for Casey? We've never had that brotherly-sisterly feel, but why am I just now figuring all of this out?

"Listen, Derek, I love you, but I can't be second in your life, and I know now I'll never be first," Jess said taking his hands in hers, looking him straight in the eyes, tears starting to now leak from her own. "So tonight when we say goodnight, I think we just need to say goodbye. Ok?"

Derek solemnly nodded.

Jessica leaned over and gave Derek a final kiss on the cheek. "Goodbye, Derek. I'll never forget you."

All he could simply say was, "Goodbye."

He watched as Jess walked up the sidewalk to her house. He didn't mean to hurt her. He hated knowing the fact that he had hurt her, but at the same time he was somewhat happy and excited.

He now realized that he had been having all these different feelings. He had watched Casey cry and suffer and he felt anger. He was so angry at Sam for causing her to hurt like this. He felt sorrow and worry. He realized that it had been killing him to watch her hurt, and he had been terribly worried about her but didn't know what he could do to make the pain go away. He also felt somewhat guilty. If Sam had not been his best friend then maybe they never would have met, and he would have never caused her this pain. But there was one feeling he could never quiet put a finger on, until tonight. That feeling he now realized was love. Love. He loved Casey.

"I love Casey!?" he said questioningly. But as soon as he said it aloud, it made his heart jump, and he knew it was true. He had slowly fallen for his step-sister.

Now what to do about these feelings? Derek thought as he drove home.

A/N: There you go. That's the first chapter out of the way. I already have the second chapter wrote out so it should be soon. Please review!