When Watson takes the lead here, Holmes realizes he's been nervous still, expecting that he'd mostly be walking Watson through this and treading carefully, and slowly. How wrong he'd been, and he'd probably been a good deal unfair. He returns the kiss openly, unreservedly, following after Watson toward the sofa with some urgency in his step.

The only time he allows for a break in his contact with Watson is when they sit, and he returns immediately to kissing, deep and slow not because he's being hesitant or careful but because he has reign to kiss Watson at his leisure. Only when he needs to breathe does he break the kiss, and then he can't stop smiling as he leans away from Watson, unbuttoning his jacket.

"I'm a bit too overdressed for the occasion. One moment," he murmurs, shrugging out of his jacket and tossing it in the direction of his armchair. "Much better. Has anyone ever told you, my dear Watson, that you're an exhaustingly excellent kisser?"