[Considering what's going to happen him, the response makes him both happy and sad at once. No, you'll need to move on eventually and find a way to be happy... he also knows better than to say that to her. For now.]
Hey. [Takes her hand in his, his hold gentle.] You're really the one that matters most to me.
[Nobody else could need him or give a shit about him, so long as you cared about him a little.]