I have to be on drugs. To say this but maybe Xenahort is the dark chaser and that he train the other chaser. That why Terra called him Master that why he also want revenge.
Maybe but there could be world that are appear to be together. We had not been every where in the realm of darkness just only so far. The only ones that know are people that been there or born there. Or the world in the realm of darkness is half of the whole original world that split. What couldn't be saved from the darkness. The blue kh could be the view from realm of darkness of the light. The yellow could be the view from the realm of light of the darkness. They never say were it takes place. Other note the door that Xemas created was his door to twilight like the door to darkness.
I believe sora don't remember what happen but what the heart forgets the body remember. So even through he don't know his body remember and didn't allow him to say it.
