Remus nodded slowly. "I'm here," he said. And he would always be there. Despite his pain, he'd never abandon Sirius, especially when he was in need. If he could help him in any way, then of course he would, even at his own expense as he was now. There was an ache in his chest, centered within what used to be his heart.
"I'm here." He repeated the words, in an attempt to soothe and comfort the other boy. He didn't know what happened, and part of him never wanted to know. All he knew right now, was that Sirius needed him, and that was enough to make him stay.