Since so many of you requested for this fic to become a multi-chapter story, I decided to add to it! I'm not sure exactly where it'll go or how often I'll update it but I promise I'll do my best not to disappoint. Thank you all for the super sweet reviews, I get a huge smile on my face whenever I see I have a new one so please keep reviewing as I continue the story! I also started another Dasey fic called "Dance Recital" which I'm really proud of and I would love if y'all would check it out!

It was dark when Derek opened his eyes. As he sat up groggily, he realized that Casey was still in his bed next to him. Memories from earlier that day flooded back. Practically carrying her to the car, his phone call with Nora, holding her hair as she was sick, his hand on her back…

He immediately glanced down, grinning slightly as he saw that the back of her shirt was still pulled up halfway with her lower back exposed. His fingers began tracing patterns on her skin, exploring her back and hips. Despite her skin burning with a fever, she began to shiver. Begrudgingly, Derek pulled down her shirt and covered her with his comforter once more. It was so nice being able to be with her, look at her, touch her without having to feign disgust at being around her. Tucking her hair behind her ear, he smiled sadly as he remembered that George and Nora would be home tomorrow and he would have to resume his role of obnoxious step-brother.

He mentally shook himself, forcing his eyes away from Casey. She was his step-sister. His annoying, aggravating, keener step-sister who wasn't all that attractive if you really look at her (or so he tried to convince himself, anyway). Him taking care of her was just him being a brother. He did the same for Marti, after all. And the forehead kiss was entirely platonic. He was simply trying to take care of her until he could force the job off on someone else. Pushing himself out of bed, he stomped down the steps and threw himself on the couch. He flipped through the channels until he found a hockey game and lost himself in it.

Moments or perhaps hours later, he heard footsteps approach the bottom of the steps.

"Derek.." came Casey's faint whisper.

"Hang on, Case. They're about to win this!" Derek yelled, his eyes glued to the screen. The game was nearly over and his team was so close to winning.

"Derek.. I don't feel.."

She never finished. A loud thud from behind him made Derek finally turn around.

"Case, are you okay-" he began but quickly fell silent in shock as he saw Casey's collapsed figure sprawled across the floor. His heart began pounding as he looked around frantically, unsure of what to do. Casey was the one who insisted on getting her CPR certification, not him. The worst he had ever experienced was when Marti fell off her bike and broke her wrist, and even that was nothing compared to this.

As the initial shock began to pass, he knelt down next to her and checked her pulse. He felt a weak beating underneath his fingertips as he pressed them to her neck. Breathing out a quick sigh of relief, he scooped her up in his arms as quickly and carefully as he could and debated whether to call an ambulance or drive her to the hospital himself. Reasoning that the ambulance would get her medical care more quickly, he laid her on the couch as gently as he could and sprinted for the phone.

After lots of stuttering, he managed to choke out his address before insisting that they hurry up and slamming the phone down once more. He began pacing up and down the living room, throwing panicked glances at Casey's limp body every few seconds. What could have happened, he wondered. Surely a stomach virus wasn't enough to make her this sick. What had he done, what hadn't he done…

A loud knock on the door caused him to jump. Swearing under his breath, he ran towards the door as it opened. Two EMT's rushed in and immediately spotting Casey, began loading her onto a gurney.

"You'll want to follow us in your car so you'll have a way to get home if you need to," said one of the men as they began moving her towards the door. Unable to speak, Derek merely nodded and picked up his keys before promptly dropping them. Swearing again at his shaking hands, he snatched them off the floor and bolted out of the house.

"Casey McDonald!" Derek yelled at a nurse, banging his fist on the desk counter that separated them. "She came in an ambulance after passing out on the living room floor! She has brown hair and blue eyes and she's wearing these ridiculous pink pajamas pants with rabbits on them! I did what the EMT's said and drove here separately, against my better judgement I might add, now where the hell is she?"

"What is your relationship with the patient?" asked the nurse sternly, obviously irritated at Derek's rudeness.

"She's my step-sister, why the hell does it matter? WHERE IS SHE?" he yelled, raking his fingers through his hair.

The nurse began to retort but was interrupted as a doctor in mint green scrubs entered the room.

"Derek McDonald?"

"Venturi," he corrected her. "But I'm here for Casey McDonald, she's my step-sister."

"My mistake. This way, Mr. Venturi," said the doctor kindly, motioning for Derek to follow her. Three hallways and several rooms later, the doctor stopped in front of what he assumed was Casey's room.

"Your sister's fainting was a result of severe dehydration. We are currently providing her with fluids through an IV. You'll be able to take her home soon," said the doctor in a soothing tone.

"So.. so she's okay?" whispered Derek, his voice breaking in relief.

"Yes, she's okay," replied the doctor with a reassuring smile. "Do you have parents you can call?"

"Our parents are out of town for the weekend, hence why I'm here instead of them. She was throwing up for most of the day and had a fever, I should have known to make sure she was drinking more-"

"It's not an uncommon occurrence, Mr. Venturi. We see patients in here all the time due to dehydration after a stomach virus or food poisoning. This isn't your fault."

Derek nodded, running his fingers through his hair once more. Entering the hospital room, he immediately pulled a chair next to Casey's bed. Grateful that she was unconscious, he took her hand in his as his vision began to blur with unshed tears. Swiping at his eyes with his wrist, he whispered "I'm sorry, Case."

Despite the doctor's reassurance, Derek couldn't stop nauseating guilt from overwhelming him. He wasn't stupid, he knew that throwing up could make you dehydrated. Hadn't his mother always told him to increase his fluid intake when he was sick? Yet here he was, in a hospital room, because he wasn't able to take care of her. She had tried to come to him for help but he didn't listen because he was too distracted by a hockey game. A hockey game. The thought sickened him.

From this point forward, he vowed to himself, he would never let something like this happen again. He would protect her, just like he should have been doing all along. Even if her step-brother was all he would ever be, he wasn't going to let anything hurt her ever again. It wasn't until a tear slid down his cheek did he realize that Casey was the only girl to ever make him cry.