It is both a metaphor and complete, utter reality. Occasionally there is overlap, though I understand how this particular one would be bewildering.

[Nobodies lived very odd 'existences'. Explaining them to someone who seemed to have no grasp at all of what's coming is a bit difficult, especially as Xemnas doesn't know how much background Riku actually has.. or if he has amnesia, or if this is Vexen's replica, or what.]

In either case, it's irrelevant now. I am not as I was, and intend to not return to such a state again. There is something terribly addictive to humanity that I can't quite put a finger on.

[He sounds a touch amused at the idea, though.]