[ Naoto shifts even closer, pressing himself up against Sion's stomach in response to Sion's movement and moving his hips a little, while the hand holding Sion's tightens and squeezes and clings. His hand on Sion's back stays there; his fingers spread out or flatten or curl up and at some point Sion does something that's enough to get Naoto to drag his fingernails up and leave bright marks across Sion's shoulderblade.

His face though is probably worth paying most attention to. More than any other reaction it's his expression that most effectively conveys what he likes more or likes less, and every time he makes eye contact it becomes abundantly clear that he is enjoying himself immensely. ]