Sirius had been kissed before, of course, and he had kissed girls - lots of girls - in his quest to find the perfect person that he was meant to love. But none of those kisses had felt like anything, although the girls came away sighing happily. They had never affected him, leaving him wonder what was wrong with him.
But this was different. Very different. And this was Remus.
Sirius' response was instantaneous and natural - he pressed his own lips back against Remus, feeling a surge of electricity shoot through him such as he had never experienced before. His hand went to Remus' arm, as if to anchor them, as he simply melted into that very wonderful kiss.