"When I figure out a way to do it, if you still feel that way then we won't do it," Sora points out. He is going to keep using that kind of language, 'when' instead of 'if.' They are on a totally new world, Sora somehow came back from what had happened to him, and there were a bunch of Keyblade wielders running around this moon.

Finding a way to give Vanitas the ability to be his own person doesn't even feel like the most impossible thing he's ever set out to do, not when they already have so much luck on their side.

He's ignoring all of the ways their current situation isn't so lucky, of course, but he's always been really good at that.