Him running wouldn't be completely out of character. Old habits die hard, especially in extreme situations.
@Js1a231 She always regretted bullying Reiji, but her feelings are platonic. Ghost Girl only had Reiji meet her to clear up some of his issues, not to hook them up.
I think he will say something like: no thanks I don't plan to have someone because I prefer to be alone. I have great expectations that this will happen.
What will he do ? He will jump by the window and try to run away from this hazardous situation. Then he will leave town and try to live in the mountain as an hermit in order to never ever again see these strange people. Or so I think. What can't I dream a little please ?