This is my first published fanfiction! I hope you like it. Spoiler through the end of season 9 because it takes place after Dean is turned into a demon.
"Dean!" Cas shouted, trying to get through to him. He never knew that the First Blade would change Dean into a demon. If he had, Cas never would gave let him near it. "Dean," Cas pleaded, ducking below a crushing blow. His stolen grace was fading fast. He would never win this fight.
The First Blade had just recently turned him into a demon. The demon in him was clever. Very clever. His skills from hunting mixed with the skills a demon possessed made him impossible to beat and he knew it.
He swung the knife at Cas again, but he moved backwards just in time. Cas then lunged and punched Dean in the gut, shouting his name with tears in his eyes.
"Dean! Listen, please!" Dean swung his fist at his jaw and Cas was struck with overwhelming clarity; he could not win. Then he stopped shouting Dean's name. He stopped trying to get him to see. He gripped his angel blade tightly and closed his eyes so he didn't have to see who he was killing.
But when he closed his eyes, he opened them almost immediately because Dean had just leaned in to kiss him. Cas was surprised at first and tried to pull away. But his eyes fluttered and he leaned into Dean's mouth. He never knew Dean liked him like this. Was this the same Dean who would always bitch about personal space? The same Dean who had never taken an interest in him beyond wayward angel?
No, Cas thought. This isn't the same Dean. He tried to pull away from the demon, but he felt the cool blade of his knife against his gut. Then he could only feel pain.
Cas sunk to his knees, pulling his mouth away from Dean 's.
He gasped and fell backwards, looking up into Dean's wide smirk and black eyes. The pain was so unbearable that he wished Dean's hit had been fatal.
"Why did you fight me Cas?" Asked Dean. He leaned down and took Cas' hand. "We could have been on the same side."
"No," Cas tried to wrench his hand away only to grit his teeth in pain. The grace he stole was healing him, but just barely. "You're wrong,"
Now it was Dean's turn to be surprised.
Cas said in a gasping, bloody voice. "I would . . . never . . . fight on that side."
Dean dropped his hand and Cas collapsed. He lifted the blade to deliver the killing blow.
Lying in the ground, Cas mustered up the energy to ask one more question.
"What about Sam?" Dean loosened his grip on the blade. Cas had found his weak spot and kept pushing. "What will he do without you?"
Dean started to lower his hand, his eyes switching from black to green to black again.
"Sam needs you. Dean-I need you." Cas looked up and locked on Dean's eyes. Dean's black eyes. If only they would stay green.
But he started to raise the blade again and Cas closed his eyes to prepare for the killing blow . . . but it never came. Slowly, he opened his eyes. What he saw made his blood run cold.
Dean had thrust the knife into his own stomach and was bleeding out. The demon in him was trying to fight the injury. But it would never win.
"Dean!" Cas shouted. He used some of the remaining grace to take away his own pain. He was still going to die, he wasn't strong enough to stop that, but he didn't want to feel the pain and hurt Dean had caused he moved towards Dean and tried to do the same thing.
Dean's bright green eyes looked up at him and he shakily latched onto Cas' arm.
"Don't do it. . . I deserve to feel . . . like this." Every word was a punch to the gut for him. It hurt so much to talk.
"Why did you do this?" Asked Cas. He applied pressure to the wound, even though his attempts were futile.
"The demon . . . It was the only way. . ." Dean gasped out. Tears filled his eyes and threatened to leak out.
"It'll be okay," Cas whispered soothingly. "It's okay." He leaned down and kissed Dean's foread.
They lay like that until Cas couldn't stay upright and fell to lay down next to his dying friend. At least they would die together. Cas whispered calming things, occasionally pressing a kiss to his cheek or forehead, and Dean struggled to gasp for air.
Eventually, Dean was so far gone that Cas couldn't even pretend that he would survive.
He leaned over one last time and placed a kiss on Dean's lips. This kiss was sweet, tender even, nothing like the rough one Cas had gotten when the demon kissed him. Dean kissed back, too, and hot tears fell from his eyes.
"I love you Cas," he said.
"I love you Dean," Cas said.
Dean tried to say something else, but he knew it was over. And he let go of Cas' arm.
Cas cried for Dean. He cried until he couldn't any more. He cried until he had to lay down again, and he stopped breathing with Dean in his arms.