Kingdom Hearts in KH2 ending?

It is unclear how Ansem the Wise ends up in the realm of darkness after the Kingdom Hearts encoder explodes, but I am unclear on another part of the ending in KH2.
Xemnas and Organization XIII seek the power of Kingdom Hearts to be true beings and to rework the universe with its unlimited power and knowledge, but it was to my understanding the Kingdom Hearts lies in the Realm of Darkness.
My question then is, why is Kingdom Hearts floating above The World That Never Was? TWTNW exists in the Realm In-between if i understand the story correctly. Does that mean The World That Never Was is close to the Realm of Darkness, allowing Kingdom Hearts to be visible from the Castle That Never Was?
I am just confused on this little bit, maybe I am overlooking something simple and digging too much into the story, but I would like some sort of clarification.

 

yeah, that is a possibility. I read on the kh wiki today that as Xemnas consumed the remains of Kingdom Hearts, the worlds presented Riku and Sora with the Door to Darkness allowing them to enter and face Xemnas. The worlds had this ability out of their desire for Sora to stop Xemnas, and this would explain why Sora and Riku ended up in the Dark Margin.