You can also read this little fluff nugget at A03 here.
Leaving was complicated. Apparently one cannot just leave. “I miss my wings,” he muttered as he rifled through some papers on the table.
Dean stood off to the side, doing nothing, just watching him. Cas looked up and realized the impact of his words. Of course Dean would blame himself for even that. It never seemed to matter how many times he stressed to him that not everything was his responsibility. Some things can’t be fixed with mere words.
The last of the papers were gathered into a folder and slid into the medium sized canvas bag. He would be able to carry it onto the plane and not worry about the baggage business that Dean had talked about. He had a small laptop as well. Sam had set it up for his journey.
The bag also contained clothes. Dean had suggested it. “You have to have clothes. People will think that it is strange if you go halfway around the world with just the clothes on your back, some papers, and a laptop.”
“I only have these.” Cas had thrown out his arms as if putting himself on display was necessary to make the point. It wasn’t. Everyone knew what he owned. Dean had laughed, a short rumble of acknowledgement and pulled him off to his room. He took Cas’ bag and set it on the edge of the bed. He didn’t comment much; he just opened a drawer and pulled out some clothes.
Cas saw a shirt, plaid with light sunset colors paired with blue. He wanted Dean to pick that one for his bag. He didn’t. He pulled out a grey t-shirt which Cas thought was rather dull. Dean’s lip curled up into a little half smile as he pulled out another t-shirt that had the words, ‘Highway to Hell’ blazoned across it. He turned to Cas then and noted the furrowed brow. “Just kidding,” Dean had said as he put it back.
Cas stepped closer and rested his hand on the sunset of plaid. It had pinks and a little white. He had liked the way that it had looked on Dean. It made him seem softer. While Sam and Dean had been on one of their hunts, he had worn it. He had been careful though and was sure that no one, Dean in particular, had guessed at the intrusion. Cas started to pull it from the drawer. “This one.”