Wow! I love the storytelling in this, as well as the craft! Remus has that "huh?" look in the first panel, and Sirius has his eyes closed, in this determined "I'm going to do this" kind of way. I think they haven't kissed before, so in the second panel, they're looking at each other and I deciding it's okay. Then the third one is all relaxed and sweet, and after that the urgency builds up again.
That last panel is altogether hot, but I like it as a set.