Derek is expecting the joke, but he definitely wasn't prepared for what comes after. He knows that he isn't the warmest of people, and not the easiest to get along with. But Thomas means it when he says that he would need Derek, and that he's comfortable around him. This knowledge brings with it a whole surge of emotion that Derek has no idea what to do with, not at first.

All he wants is to be needed, to find safety and companionship. He has friends here, more friends than he ever thought he could have. He knows they like him, and maybe they even need him, but to hear it said is something else entirely. He stares at Thomas, a little stunned, but he can't help the way that the corners of his mouth quirk up into a smile.

"For all the same reasons," Derek assures him, because the words don't flow so freely with him. It comes from years of emotional constipation, and trying his best to numb himself to the world. Talking about what he's feeling is a herculean effort that he hasn't quite grown accustomed to yet, if he ever will.