[He's quiet, just letting her speak - a few times perhaps wishing to interject, but not wanting to interrupt her. So he lets her speak everything on her mind, listening respectfully (and quietly biting his tongue to hold back a small smile of the endearing thought of not being casual, but...)]
[...]
[waits until he's certain that she's paused for now, before he's kneeling down in front of her, humming thoughtfully - because whatever he's not afraid of your brother (although perhaps he should be) but that last part in particular rings pretty true of some of the things Aramis has told him in the past, some things that Robin has hinted at.]
I'm afraid I have to disagree, milady. If I don't deserve to be a demon, I don't believe you do, either. [...] I've seen some of your memories, you know. [Through that magic, with those feathers before -- so her backstory isn't as shocking to him as it perhaps could have been] If I wish to know you, that's my choice... I'm a soldier. I can take care of myself. Unless you'd rather I do stay away, then I can't disobey your wish.
[...] I won't bring this all up again to you, if that's what you wish, as well. But I can't forget. Even if I'm... more casual about these things than you are, it's never something I can just forget about. It isn't nothing to me, even if there was all this magic involved. [The demon version of himself definitely felt something beyond just platonic feelings, after all.]