AN: This oneshot takes place during Season Five, Episode Eighteen, Point Of No Return, when Dean sees Castiel looking at him from outside of Bobby's panic room. 

Sam followed Dean through the doors of Bobby's panic room, while Castiel waited outside. Dean looked up from his spot in the panic room to see Castiel, and what he saw took his breath away.

Castiel was looking at him with an expression on his face that Dean had never seen before. He had seen all of Castiel's expressions in the time that they had been friends, from the tilted-head look that he gave when he was confused about something, to the heartfelt look that he sometimes gave Dean when he sensed that Dean was upset about something. For just one, beautiful second, Dean remembered when Castiel had told Sam that he and Dean shared a "more profound bond", and how Dean's heart had skipped a beat at his words. 

Dean remembered the first time that he had saw Castiel, when the angel had appeared to him due to a summoning, after he had been forced to blind Pamela. Despite the then dangers because of his unfamiliarity with anything as powerful as an angel, Dean couldn't help being captivated by Castiel. As he slowly advanced towards Dean and Bobby, Dean thought to himself that he had never seen anything so powerful, thrilling, dangerous, and downright sexy in his entire life. 

Ever since that first meeting with Castiel, Dean had felt some sort of an unusual connection to the angel. He quickly became Dean's favorite person, second to Sam, and Dean found himself thinking of Castiel much too often. He longed for the powerful angel to be a third wheel to Sam and himself for the rest of eternity, but he knew that Cas had important angel business to take care of in Heaven. Still, every moment that Castiel was gone, Dean felt incomplete - less than whole. 

However, when Cas was there with him, Dean felt as though the last piece of himself had fallen perfectly into place.

It was a feeling that haunted Dean.

Dean was suddenly snapped out of his memories, and his eyes returned to Cas's face, which hadn't changed since he had last looked. That sultry vixen look was burning an edge into his mind. Dean wanted so much to just walk over and hug the angel, but he knew that he shouldn't do so in front of Sam, especially without justifiable cause to do so. 

So, Dean, activating his flirtation mode, said to Castiel, "You know, not for nothing, Cas, but the last time someone looked at me like that, I got laid." 

Dean could tell from the change in Cas's face that Cas had understood, at least in retrospect, but was unsure of his mistake. Therefore, the expression on his face did not change very much at all. 

Dean gazed into the electric blue eyes of his angel, taking in every inch of the sultry look on Castiel's face. Something about that look made Dean want to run up to Castiel, hug him tightly, and kiss his lips fiercely until their veins were pumping burning, white-hot desire straight to their hearts, which were so meant for each other.

Dean was interrupted in his thoughts by Sam quietly saying from beside him, "Uh, Cas, why don't you go keep an eye on Adam?" Castiel nodded and looked at Dean for confirmation. 

Although his heart was aching for Cas to stay with him, Dean nodded slightly. Then, before he could change his mind, Dean smiled at Cas and shot him a flirtatious wink. 

He didn't know why he was suddenly acting so gay with his best friend, but Dean wasn't about to stop. He absolutely loved Cas and loved spending time with him. It was the only thing, in those days, that filled him with that much joy. 

As he was thinking about that, all Dean wanted was to kiss Castiel with everything that he had and more. He wanted to kiss Cas until their lips were sore and they could barely keep their hands off of one another.

Dean wanted to kiss Castiel.

After he finished talking with Sam, that is exactly what Dean did.

While Dean's lips were tightly sealed to Cas's, Dean realized something.

Dean realized that he was in love with Castiel Novak.