Castiel knew it was over the second Dean turned to him and shouted, “Lucifer has Sam. He has Jack. Cas, I don't have a choice!” He knew that Dean had made up his mind, that Dean, after everything, was going to say yes.
There was one thing that Dean would give up everything for, and that was Sam. Cas and Dean had watched in horror as Lucifer stole Jack’s power and taken off with Sam and Cas. They both knew what kind of power Lucifer had and what he could do. And Castiel knew that Dean would be willing to do anything to protect them, including giving his own vessel and free will to Michael.
Castiel’s heart broke as he looked in Dean’s eyes and saw the pure panic but he barely had time to react before Dean turned back to Michael, “If we do this, it’s a one time deal. I’m in charge. You’re the engine, but I’m behind the wheel, understand?”
“Wait!” Cas blurted out and lunged for Dean’s arm.
“Cas, there’s no time. You know what Lucifer can do.”
“Dean, two minutes. I need two minutes to talk to you before you do this.” Cas implored his friend with everything he had.
Dean softened when their eyes met, “Fine,” he grumbled and he pulled Cas a few feet away into the library. Dean closed his eyes, and outward sign of the internal pain he was fighting. “Cas…”
“Dean, all we’ve fought for…”
“Do you have a better answer here? Sometimes you just have to go with the best worst solution.”
Dean’s eyes filled with tears he would never let fall and they begged Cas’ for understanding.
“Dean, you don’t know what you’re asking. Being a vessel it’s… it can be torture.”
“Yeah, I call that Tuesday, Cas. You know how many times I’ve been tortured?”
Cas’ heart ached for Dean. He knew what this man has endured, in hell, in purgatory, on earth. He remembered vividly the attack on hell, slaying demons as they did unspeakable things to human souls trapped in damnation, things they first learned from Lucifer and his fallen angels, methods that had been used on Cas himself in heaven. Yes, he knew first hand what kind of torture Dean could endure and he hated that this Righteous Man, his friend, deserved so much better than the pain this life had dealt him.
Cas put a steadying hand on Dean’s shoulder. “I know, but this is different. Michael is powerful. When an angel takes a vessel, they can choose to protect that vessel’s soul as I did with Jimmy. But don’t expect such mercy from Michael. He could destroy you. And how will you expel him once you have saved Sam?”
“You did it! So did Sam.”
Dean is right. He and Sam both did the near impossible and overcame the archangel who was possessing them, even if only for a brief moment. How? Neither of them should have had the ability to overpower the most awesome force of Chuck’s creation. What had given them the momentary strength they needed to take control from Lucifer? And that’s when it dawned on Cas that it was Dean. Every time, it was their love for Dean that empowered them. This broken man standing in front of him in anguish held so much love inside of him that the sheer force of that love had overcome Lucifer himself.
And love would be the only thing strong enough to save him from Michael.
Castiel mustered all of the courage he had and pulled Dean forward, slamming his lips against Dean’s. It was quick and rough and over too fast as Dean broke the kiss, shoving hard against Castiel’s chest to separate them.
“What the fuck, Cas?!” Dean growled.
It had failed. Castiel’s small hope that Dean would return the love he felt was shattered. “Dean, I’m sorry, I-”
“Don’t!” Dean interrupted, pointing at him, “Just don’t. You goddamn bastard.” Dean dragged his hand down his face and turned his back to Cas taking a step away before looking up at the ceiling and taking in a long breath.
Oh god, Castiel had ruined everything. He had stepped across a line he knew Dean would never want and now his friend, the most important person in the world to him, would hate him for it. This might be the last time he would ever see Dean alive and he had done everything wong. Again.
But then Dean turned back around and stepped into Castiel’s space, “Why?”
“You… you’re going to be trapped inside of your own mind. You’ll need to fight.”
“What the hell does that have to do with anything? You know what I’m asking, Cas. Why did you kiss me?”
Castiel shifted on his feet uncomfortably, trying to think of a way to explain this to Dean, of a way to make it right. “Because I don’t believe my brother will let you go. Because I know that the only thing that will give you the power to take back your vessel is love and I wasn’t going to let you face that without knowing that… that I love you, Dean. I have always loved you and I always will. And whether it takes you a day or a thousand years to break free, you need to know that someone who loves you will be waiting and fighting for you every day.”
Dean looked dumbfounded, blinking several times before letting out a hysterical huff of laugher, “Jesus Christ, Cas. Ten years. Ten fucking years and you wait until now to let me know this?”
Castiel tilted his head and squinted into those green eyes, “How could you have thought otherwise, Dean? I rebelled against heaven, against my family for you. I have chosen you over everything time and again. I return to you always. And I know that you don’t feel the same way, but I need you to have some hope to hold onto when Michael has you trapped. I’m sorry if I overstepped.”
Dean shook his head, “No. Don’t apologize, Cas. Jesus, I’m not mad that you kissed me, only that it took so freaking long. And now...” Dean sighed and took one step closer to Cas, wrapped his hand around the back of the angel’s neck and pulled him in for another kiss.
This time it was different. It was soft and passionate, Dean tilting his head as his lips moved against Castiel’s. It felt like nothing Cas had ever experienced, to connect with Dean in this intimate way and to feel the relief of knowing that Dean returned his affections.
When Dean broke the kiss he kept his face close to Cas’, foreheads touching as he whispered, “God, Cas, why didn’t we do this sooner? What if… what if this is all we have?”
Castiel brought his hand up to Dean’s jaw, thumb caressing his cheek. “It isn’t, Dean. Do you know how I overcame Lucifer, even if it was briefly? It was you. It was my love for you. You can do the same. Fight, Dean. Keep fighting to get back to me, to Sam and to Jack.”
Dean pulled back just a bit, breaking their connection just far enough that Castiel could see a tear drip down his cheek as Dean angrily swiped it away. “Fuck… I’m scared, Cas.”
“I know. But you are the strongest man I have ever known. You will save Sam, Jack, and your world. And you will fight your way back to me. Dean, listen to me now.” Castiel brought his hands up to hold Dean’s face firm and force him to look straight into his eyes. “If Michael fights to control your vessel, don’t give up. Know that whatever Michael does in your vessel is Michael. Nothing is on you. And if you want to get back to Sam and me you will need to remember us, remember everything good, remember the love you have for Sam. Love is more powerful than anything. Follow it back to us.”
Dean nodded and dipped in for one last quick kiss. Castiel could feel the tremor of Dean’s lips against his own as they pulled apart. He watched helplessly as Dean turned away from him, walked towards Michael and his world shattered as Dean said the word Castiel had dreaded since he first realized how much he loved him.