While doing some translation research, and background info tracking for the latest updates to this website, some rather interesting parallels were suddenly revealed to me, it seems to me, about the nature behind Arashi's interactions with Sorata. And a lot of it has to do with her mother. Some of this is blatant plot points and some of this is conjecture. This will not be spoiler free, so you have been forewarned.
An obvious one is revealed in Arashi's side story. Unwilling to eat because to eat is to live, Arashi was coaxed back to "life" by her mother's friend Kaede, much in the same way that Sorata did for Kamui. It was at this point in the story that her feelings started to become more visible on the surface.
But an interesting parallel lies in a fraction of a conversation, also found in the side story. When Arashi's mother died, she told Arashi that she had to die, so that Arashi could live. By Arashi's mother's words, she claims that she was fated to die for her. Remind you of somebody else?
It has become my belief that this was part of the reason Arashi was so afraid of the prophecy Sorata held over his head. She didn't want anyone else to die for her, let alone a person she was slowly growing feelings for. Her mother's death had affected her in such a profound way, that she was afraid of being hurt again, also afraid that because Sorata told her so that it would happen.
Something else to consider, and this has to do with the X TV anime series. Near the end of the series, Sorata does die, protecting Arashi from Fuuma. His last words to her were to keep living, the exact same thing Arashi's mother had said to her as well.
We'll have to wait and see where the manga takes us, but if Sorata dies, and if he utters those same last words, it will be something to ponder.