Well, You Tube muted it, but you can get it on AMV.org, here: (please note that the file is huge, so download takes a while) http://www.animemusicvideos.org/members/members_videoinfo...
It's an awful shame because I worked really hard on this :(
Story: (very, very long.)
(The only change to the cannon is that the members of Organization XIII all killed each other a few months ago. Roxas is the only survivor because he coincidentally left two days before the fight broke out. He is currently living in Twilight Town because it seemed like the safest place to escape to at the time. Hes very happy and has several very good friends there)
One day, Roxas begins to have hallucinations about a boy named Sora. He tried to ignore the hallucinations at first, but he began to lose memories of his time in the Org. Still, he isn't sure of what to do. One day, he suddenly becomes Sora. During the vision, he sees a little blonde girl, sitting in a room he knows is in the mansion in Twilight Town.
Later on, when he wakes up, he goes to see her. she tells him that as long as Roxas stays in Twilight Town, Sora will have more and more power over him, until Roxas loses his identity altogether.
Obviously, Roxas decides to leave. He goes to tell his friends that hes leaving, but they go right through him Suddenly, Roxas is able to recall everything that happened during his year with the Organization, the way that there's nothing left for him outside of Twilight Town (and he notices the similarities between his friends and Sora's)
He thinks and reflects on his way up to the station, and before he knows it, hes right in front of the train that will take him to Yen Sids tower and his freedom. However, he realizes that he cant leave. Hes going to continue to stay in Twilight Town until the rest of his days.
When Sora awakes, his head is filled with odd memories: a boy and girl about his age. He ignores the memory and goes off find Riku and return to the islands. Once he, Riku, and Kairi are back together, he understands everything that happened. And he sees something that even Roxas didn't: that now Roxas, Axel, and Xion are back together too. (Yes, in this story Axel becomes part of Riku. I like that theory :D)

All credits are in the video (less info)