Andre is like that to everyone in general due to past issues. However he had it drilled into him from a young age to be a good person to women. Though he doesn't strictly live by that he does give girls a bit more leeway than boys though only by a small margin. And he isn't hostile to anyone who just goes up and says hello to him he'll say hi back as long as you don't keep poking him or do so in an way that he finds obnoxious.
I see... Well at least he is nice to people when they acknowledge him. Shinrei is the complete opposite unless he feels nostalgic. That is the only time his other side of himself rises to the surface otherwise he is cold by nature and hides himself under that thick hard cold shell of his.
Well, I think you saw that Shinrei has a more human side to him when he's alone. When he's around people especially crowds he shifts into his isolation state where he shuts everything out acting like what is around him that would distract him doesn't exist. As I revealed, he isn't really that flat and does have a human nature to him but his shadows of his past tend to keep under quarantine hence his mysterious nature, dark appearance and his cold attitude.