Trowa does not startle. His eyes do slide over to Quatre, though.

He also doesn't smile, but one of the nice things about conversing with Quatre is that Trowa doesn't actually need to move his face to have the underlying sentiment understood.

He turns a page, refocusing on his book, and settles back a millimeter more into the sofa. (If this puts his shoulder a millimeter closer to Quatre, too, that's . . . probably not a coincidence.)