Little is known of the ritual itself, apart from the vows being uttered in Enochian, the angel's native language; not even the wording has been communicated to humans. Some theories claim that it binds indeed the graces of two angels together, but none have adequately explained the meaning of this scenario.

John Drake, Theories and Speculation: The Truth About Angels, p.211

He barely paid attention to his students that day, but he decided that no one could blame him for it. He'd soon have all the time on the world to bestow on classes and his brother and his friends. Let him feel sad at school for one day. Thankfully it was Friday; he'd have all weekend to nurse his broken heart and return to work and life with a happy attitude, acting like he didn't care that Cas was off to find his soulmate.

He left hastily so Charlie wouldn't try to talk to him and went shopping.

It was the last time he bought Cas' favourite beer – another last time, another last time – and Dean almost tore up in the stupid isle of the stupid store, and he drove home going way above the speed limit but God damn it, he needed some release before he had to pretend for the rest of his life.

He had never given Cas a key because the angel had never shown that he'd like one, and he was glad for it now because that meant Cas wouldn't be awkwardly handing it back.

When Cas' knock echoed against the door, he took one deep breath. Just one.

The last time.

Cas wore the same suit and trench coat he had worn the day they met and hadn't laid off since, Dean believed. The clothes looked as brand new as they had in the Laundromat ten years ago, and Dean told himself that the look of an askew tie shouldn't make him want to cry. Nothing of this should be special because it was the last time; if he didn't let it be special to him, it would hurt less.

He didn't really believe it, but he smiled at Cas as he heard the old greeting "Hello, Dean" regardless.

Cas looked... haggard. Worn down. A little sad, maybe. Dean knew he left earth reluctantly. He loved nature, he loved animals, he loved flying, soaring over the skies.

He refused to believe that Cas was sad because of him. He was nothing to cry over.

"Hey, Cas. Want a beer?"

Cas nodded without really looking at him. That was strange. Cas had always had the habit of staring at Dean, to a degree that Charlie had once called "creepily endearing". He'd never avoided Dean's eyes.

As he handed him the beer, the thought that Cas knew flashed through this Dean's mind.

No. Oh God please no. He didn't want to have this discussion. Ever.

But then, Cas, staring at the beer bottle, said, "There is something I'd like to ask of you, Dean."

"Anything".

He answered before his mind had caught up, but he knew he was true. Whatever Cas wanted him to do, he'd do it. As long as Cas was still here.

"You've shown me much, and I'm very thankful..." Cas had never sounded so timid before. What could he possible ask to make him feel that self-conscious?

"But there is one thing."

And he looked at Dean, completely serious and calm, and continued, "I have never participated in sexual intercourse".

He opened his mouth but closed it again when he realized he'd forgotten how to speak. Was Cas asking what he thought he was asking? And if, was it right to do it? Cas wanted to sleep with him. But he had no idea why Dean would agree, wouldn't know that he didn't do it as a favour, but because of thousands little stolen moment when he'd looked at his friend and seen everything he'd ever wanted...

But he could have Cas. He could have this, and in years, when he was feeling sad and pathetic and alone, he could have the memory to keep him warm.

In the end, the decision was easy.

Cas was relieved when Dean didn't get angry or seem particularly shocked. He had thought about his request for a long time, and had always known that should he utter it, he would do so only on his last night, during the last few hours he'd spend with Dean.

It was wrong, utterly wrong and despicable, to betray his friend like this. Dean had been nothing but good to him, had shown him all there was to humanity, he owed him countless happy hours; and yet he was lying to him.

He didn't want to spend the night with Dean because he wished for experience.

He wanted to because he loved Dean.

He had for almost as long as he had known him. Not a single moment passed in which he didn't wish to mingle his grace with the bright soul of the wonderful man who had decided to befriend a lost angel.

But Dean didn't want him, couldn't want him that way. While he had eventually admitted that he was attracted to both genders – and had thus inadvertently nourished Cas' useless hopes – he'd never given him any indication to think that he was interested in Cas.

Plus, even if he had been, there was no way of knowing for how long, or whether he'd even wish to be mutually exclusive; for humans, relationships meant a lot of different things; and Cas wanted nothing less than to mate Dean.

Heaven, immortality, his siblings – it meant little to him. He'd always been an outsider, always wishing to see the Earth, ever since he had been born; and when he'd tried to put his feelings into words, Dean had laughed and called him a mermaid and Cas still didn't understand why.

But Dean didn't wish to mate, and Cas had just asked him to give himself to him, to pretend for a few short hours before he had to leave and search for someone he would not find in Heaven, but who would live upon earth and probably soon forget about the angel who'd been confused by washing machines.

Cas sometimes thought Dean hoped that they'd eventually see each other again, once he was mated and allowed to return to earth. But it would never happen. The only being he would ever love enough to desire the bond was beyond his reach.

This was the last time he would ever be with him.

He should have know that Dean, who didn't like to talk about his feelings, would prefer to act instead of discussing things further.

The kiss took him by surprise, but even with his limited experience he was able to reciprocate.

He had never understood the humans' need to use metaphors and similes. He finally did.

Dean kissed him and he saw stars.

Long before it was over, long before desire had pushed them over the edge, before they had stopped caressing each other and lay on Dean's bed panting, Dean knew it had been a mistake.

He would never forget a moment of this, would never forget how Cas felt against him, every move, every breath ingrained in his mind, his heart.

No one else would ever come close to this.

No one else would ever feel this good.

He closed his eyes and willed himself not to cry. Cas took him in his arms, put his wings around him. He buried his face in Cas' neck, somehow keeping his muscles from trembling, betraying him.

"I'll miss you" he mumbled. It was the only confession he allowed himself.

"I'll miss you too" Cas answered, and Dean wished his heart hadn't soared at the words. Cas shouldn't miss him. Cas should be looking for someone, the perfect match for him, not missing Dean, who'd never deserved his friendship, much less this.

He started whispering words Dean recognized as Enochian. Maybe it was a blessing; maybe it was a goodbye.

Dean was feeling strangely exhausted – the sex had been fantastic, but he still should have been able to keep his eyes open – and Cas was gently stroking his back and still mumbling words that were strangely calming, lulling him to rest.

He knew as he lost the fight against sleep that Cas was too polite to wake him, and that when he woke up, Cas would be gone.

Cas should never have allowed himself to whisper the words of the bonding ritual into Dean's skin, a mockery of what he could never have.

Yet he had to say them once, even though Dean's soul wouldn't accept the offer, and therefore the bond wouldn't be formed. He had to say them once in his existence that would be spent loving someone who'd never considered the possibility.

Suddenly, he wished the human beliefs were true. He wished they went to Heaven when they died.

He wished he could wait for Dean.

He held him in his arms and wings and thought he'd never loved him as much as he at this moment.

His mind was growing sluggish; maybe their earlier activities had exhausted him. He didn't mind. For the first and the last time, he could rest next to the only being in all of creation he would ever love.

Dean woke up. Cas was gone.

Dean felt like screaming or crying and did neither.

He showered and ignored the missed calls and texts on his phone.

He wandered into the kitchen. He needed coffee.

The rest of his life had officially begun.

Cas was in his kitchen, buttering toast. His chest was bare, his wings almost glowing in the sunlight streaming in through the window.

"Cas?" he asked, not believing what he saw. Perhaps he was dreaming. Or he had gone insane.

Cas turned around and smiled a bigger smile than Dean had ever seen on him.

"Dean!"

And then he was being kissed, and he figured he might as well go with it.

It was when Cas breathed against his throat "My beautiful mate" that his brain caught on.

He pushed him away.

"What?"

"I said the words. Yesterday, I pledged myself to you." Cas cradled his face in his hand.

"And your soul accepted the bond. I didn't know what had happened until I woke up this morning, but that your soul clung to my grace and that we mated – it proves that you love me as I love you".

He sounded awed.

"But that - " Elation and shock fought in Dean's mind.

"But that means you'll die, Cas!"

"Yes" he confirmed, casually, carelessly.

"How can you be so calm about this?"

"Because" he said simply, "I get to live with you first".

And he kissed him again, and Dean couldn't resist the temptation, and it went on and on until he pushed him away once more.

"Cas – we have to talk about this".

"Why?"

"Why? Because you more or less angel-married us, and now you're going to live with me, and don't get me wrong, it's everything I've ever wanted, but what about you having to eat and to sleep now, not to mention that you'll age and die, and you'll need a job and – you don't even have a last name!"

Cas wings hugged him, drawing him closer.

"I do" he said softly. "The antecedents show that in a case of angel-human mating, the angel takes the last name of the human. Castiel Winchester – I like it".

"But – but – " Dean stuttered "You can't tell me that you are completely relaxed about this – "

"I am".

"But how – "

"I'm with you".

And he sounded and looked so sincere that Dean had no choice but to believe and kiss him again.

Sam got the surprise of his life half an hour later when he, concerned that Dean hadn't taken his calls or answered his texts, decided to check on him and found his brother making out with his friend – Sam supposed his brother-in-law now – on the couch.

The next day, there was a similar party to the one held a three days previously, but this time, Dean was happier than he'd ever been and Cas did not once leave his side, once of his wings wrapped securely around him.

First Angel-Human Mating Confirmed In A Century, Seventh Overall

It has been confirmed that, for the first time in a century, an angel has mated a human and thus renounced his immortality and kinship to Heaven.

This is the seventh interracial mating since the Reveal, and the third that has taken place in the United States.

Interracial mating is an extremely rare phenomenon; sources point to it taking place in or around Lawrence, Kansas.

Authorities approached for information told the press that they had been asked to simply quote one of the happy couple – "Tell them I'm a damn lucky bastard".

Lawrence Journal-World, 13th August 2015