kingdomheartsfan: Why couldn't you keep Sora's eyes both blue? Vanitas can still live in Sora's heart while both Sora's eyes are blue.

AN: As I said in the author's note, there would be changes to Sora's design differing from the original, but the different eye colour is one of the things I kept the same. (Along with the bell sleeves, and Sora's hair) Yes, it is Sora's body, and yes, Sora still does have control, but if both his eyes were the same colour, there would be less of a difference to Sora than the original.

Vanitas had already had a place in Sora's heart for some time, the Sora with heterochromia is a step up from that, because Vanitas is supposed to be more evident than before. No he is not dominant, but more prominent. Because there are barely any changes to Sora's personality, besides the occasional slip of tongue and new knowledge (tossing in a bit of craving for darkness here and there), the only way to show Vanitas' new higher awareness is by Sora's physical body. The black in his hair, the eyes and sigil are ways of quickly reminding someone that he isn't completely Sora, that there's something off. You could tell someone you can't walk, but some people don't fully comprehend "Oh my gosh, this person actually can't walk." until they see a wheel chair. A difference between hearing and understanding.

Plus, I doubt Vanitas would go into total submission, so these things are also just little ways Vanitas can show the finger to the universe in defiance. (The Sigil over Sora's heart is a way of Vanitas somewhat claiming Sora in a sense that he'll never just be Sora ever again. He has to carry Vanitas' weight, too.)

So yeah, not really my choice originally, but I still stuck with it.