Brax thinks of Fuu as intelligent, bright, and to be handled with care. She seems to both have the disposition to pry into things and a certain sort of idealism that he wouldn't care to let near some of the nastier things in his world. It's a dangerous combination, so he keeps her at arms' length. Ironically, amnesiac!Brax worries about her more, even though he is far less emotional in his expression, because he is less self-isolating.