Well, first you have to understand that normally Nobodies don't exist with their Others. Once you become a Nobody, the you that existed before is gone. There have been very few exceptions, and obviously Kairi and I are one of them.

But because I exist, right now Kairi isn't whole. And she can't live like that forever, so eventually I'm going to have to go back to her in order to make her whole again. Once that happens, there won't be a me anymore in the physical sense.