You and your questions that make me think. I think I agree with what Apa said when we talked about it; for Kamui to realize that he's still Fuuma, just a different side of him. Fuuma is just as capable of being a jerk as Kamui is capable of being nice, despite where they started out in the series. Kakyou did tell Kamui that the side a person shows to you isn't everything about them, so. That is my best guess.
You might have already said, but I am a goldfish. What's Kamui's real wish?