A/N: This is the first story I have ever written. It is something I came up with while listening to It Girl by Jason Derulo and I wrote it very quickly while the idea was still in my head. It does contain a few minor spoilers to 3x24, 4x05, and 4x07. Reviews would be greatly appreciated! Enjoy :)

Disclaimer: The characters all belong to Andrew Marlowe and the song lyrics belong to Jason Derulo.

"CASTLE!"

"Give me a second, I'm almost done!"

Kate Beckett stood in the foyer of her boyfriend's loft. She had been ready to leave for ten minutes and was losing patience quickly. She could hear a laptop slam closed and the shuffling of feet across the floor.

She watched his office door until Rick Castle's head popped out.

"Sorry, I was just finishing a chapter," He said as he reached her, giving her a quick peck on the cheek.

"Murders don't solve themselves, you know," She said with annoyance as Castle opened the closet and rummaged around for his coat.

"Just like best sellers don't write themselves, my dear detective," He shot back without missing a beat.

Kate was silent and Castle knew he had won this one. She watched as Castle pulled on his shoes.

"Ready?" Kate asked, already five feet out the door and headed towards the elevator.

"Kate! Wait up!" Castle called as he ran to catch her before the elevator door slammed in his face.

He jumped in at the last second. Kate just smiled and allowed him to pull her into his warm embrace for the short ride to the lobby.

"Great, look at this traffic. I don't need Gates on my back because I am late for work," Kate growled as she maneuvered her car out into morning rush hour traffic.

There had been no body drop wake up call and Kate wasn't used to this. She was usually already at a crime scene as the rest of New York was just rolling out of bed.

"Calm down Kate, it's New York City. Gates will understand." Castle started to fiddle with the radio, trying to find a good song to distract his aggravated detective.

Kate just started ahead with a scowl on her face.

As Castle passed over stations, he suddenly squealed like a five year old girl who had just been given a pony.

"Alexis loves this song! Yay!"

As Kate tuned in, she instantly recognized the singer's voice – Jason Derulo. It was true, Alexis had been listening to nothing else but the man's newest single for a week straight.

Kate smiled slightly as Castle started singing along without missing a beat.

"Tell them other girls, they can hit the exit check please. 'Cause I finally found the girl of my dreams. Much more than a New York Times Best Seller award, that's how much you mean to me!"

"That doesn't even flow Castle!" Kate laughed at her boyfriend's attempt at changing the lyrics to fit their relationship.

"Of course it does!" Castle defended himself as he jumped back into the song, Beckett's insult not fazing him at all.

Kate couldn't help but get butterflies as he reached over to squeeze her thigh as he sang to her:

Crazy how we fit girl

This is it girl

Give me 25 to life

As Castle went on, happily belting out the hit song, Kate couldn't help but think how lucky she was. If someone had told her a couple years ago that she would be in a car with Richard Castle singing her a love song, she would call them crazy.

It had taken them a long time to figure out they needed each other. Even after they realized that, it took her even longer to admit it to him. When she finally found the courage to tell him that she remembered what he had said when she was shot, he was fuming. But after a few days of not speaking, she showed up at the loft and looked him into the eyes and told him that she loved him and to get over her lying so they could be together. All at once, his anger disappeared. They had then spent the night proving to each other how much they meant those "I love you" confessions.

Kate couldn't help but think how close she had come to losing him. Several different times actually. It was the time he was held hostage at the bank that really forced her to open her eyes. That day had terrified her. The entire time, all she could think about was how they were going to miss their chance. It was horrible. She didn't know how she could have ever kept him waiting after she was shot. He didn't even know if she was okay. She finally had a taste of her own medicine and she did not like it at all. Castle was so wonderful and she didn't deserve him. He would do anything for her and he had waited so long.

A sudden loud horn of a pissed off driver broke Kate out of her memory. It was then that she realized that the song was over and Castle was abnormally quiet. She looked over and just as she was suspecting, he was staring at her.

"What are you thinking about, Detective?" He questioned softly, bringing his hand that rested on her knee to push a stray hair out of her face.

As Kate finally pulled out of the hectic traffic jam and into the Precinct parking lot, she quickly shut off the engine and turned to him.

"You…me…us," Kate said shyly, glancing up to meet his eyes when he was quiet.

"Good thoughts, I hope?" Castle questioned after a few moments, still worried that Kate would wake up one day and decide that giving them a shot was a terrible idea.

"Castle, you know I love you right?" She squeezed his hand to reassure him that they were okay.

"Of course I do. I love you too, Kate." Castle wished the car console wasn't separating them, desperately wanting to pull her closer and kiss her anxiety away.

"I just want you to know how happy you have made me. And thank you for waiting for me. I know I didn't exactly make it easy," Kate said, guilt evident in her voice.

"Hey KB. You know I would have waited as long as it took," Castle whispered lightly.

"I know and that's why I don't deserve you, Castle." Kate shifted in her seat and played with his hand, " I can't believe it took you being held hostage to finally wake up."

"Don't forget Serena Kay. Although I am glad it only took one attractive woman to bring out your jealously. I would have hated to have to kiss any more women to get your attention, my lovely Detective," Castle added lightly with a smirk.

Kate smiled and playfully nudged his shoulder, "Shut up Castle. It isn't funny."

She opened the door and climbed out of the car and waited for him to do the same. As he came around to her side of the car, Castle suddenly grabbed her by the waist and pushed her lightly against the car. He covered his mouth with hers for a passionate kiss. Kate went weak in the knees and she was glad Castle's weight was supporting her or she knew that she would be laying on the concrete right about now.

As Castle pulled away to catch his breath, he rested his forehead on hers. Kate looked him in the eye and gave him another short peck.

"It's a good thing I have the only woman I want to kiss right here in my arms."

Kate smiled as his ever-charming personality. And gave him yet another sweet kiss, this time pressing her lips to his for a little longer than necessary.

"I love you," she whispered, when she had pulled away once again.

Castle nuzzled his head into her neck and whispered the phrase back.

As they started to walk hand and hand into the Precinct, Castle asked "You going to tell me what all this was about Detective?"

Kate just smirked and said, "Maybe I just like having my boyfriend sing me love songs. Come on because now we are going to be really late."

As they reached Kate's desk, Castle plopped into his chair beside her. She knew he was mentally creating a list of possible songs to serenade her with when he got her alone later on. Deciding to have a little fun with him, she took out a post-it note from her desk and scribbled on it. She folded it in half and reached over to place it in front of him.

He looked up at her with sparkling eyes and a smile on his face.

"What is this, Beckett?"

"Just read it, Castle!"

Castle laughed softly and slowly opened the note.

I like Make You Feel My Love…Adele's version.

Castle laughed again and quickly pulled out his iPhone. Kate could see him opening his music app and then searching his various playlists. Once he had found what he was looking for, he turned his iPhone to face her.

Kate smiled as she read his "Top Played" playlist. Make You Feel My Love was number four.

As Castle clicked on the song and turned his volume down so only he and Kate could hear it, he leaned in and whispered into Kate's ear, "I guess we really are perfect for each other, Detective."