Well, that was definitely the response he was aiming for. Humming around him, Sirius took him as deep as he possibly could, nearly gagging when he hit the back of his throat but relaxing it instead. He was a quick learner, apparently, since he'd only been doing this for Remus for a few weeks now but apparently he was good at it. Hollowing his mouth out when Remus moaned like that, anticipating what was to come next as Remus saw stars and Sirius took in all that Remus gave him with a satisfied groan.