Kuroshitsuji - Can a demon fall in love with a human?

i, Sebastian Michaelis, have never in my life been in love to any female demons or angels likewise a human....but i have fallen for a very normal girl and i have no idea why would i fall in love with a human... but i cannot fall in love with her .. it would put her to danger if both of us fall in love with each other.... so i can never tell her my feelings..what would happen to the girl and Sebastian.