It was the greatest and scariest moment of his life. Remus had dreamt of this moment for years. Kissing Sirius was something he'd been waiting for, but never expected to happen. Even now, while it was happening, he was struck with disbelief. Why would Sirius ever want to kiss someone like him when he could have anyone he wanted? The answer was right there in Sirius' words before. You've always been the only one... Remus might not have thought highly of himself, but Sirius did.
As fast as his heart was pounding before, it did not compare to how fast it was beating once their lips met. Remus had never been kissed before, so he could only pray to the kissing gods that he was doing it right. His cheeks were flushed as his lips met Sirius' in a tender kiss. He kept one arm around the other boy, and placed his opposite hand on Sirius' knee. He made a soft sound as their lips kneaded together, but made no move to get away.