Hobbes wants to lift his arms, wrap them around Mike's waist, haul them together and get more of that friction against his dick, feel more of Mike's need against him. But it's not an option, not tonight, anyway, and he just crumbles against the unexpected kiss. It's not even that he didn't expect kissing - he simply expects nothing. He can't predict more than a few seconds ahead.

So he leans into the kiss while he has it, and makes a low, needy sound.