Well, he never minds being kissed with fervour. But it won't stop him being confused, and that's why he looks confused when they stop, his hand still on her waist.

'How would things change?'

Either she means that she doesn't want things to be weird after this, or she doesn't want things to be any more serious after this. Neither of which he was exactly planning on, but some clarification on the issue would still be good.