The game's story I like the best

When the man lost the "self" and fell down to darkness, he will be the "heartless". They are called the creature that gives concrete the darkness. And the man who has really strong heart becomes "heartless", "Nobody" will birth at the same time. They have no heart, but have memory of one's past.

Sora is a main character, and Roxas is Sora's Nobody. Ordinally Nobodies have memories, but Roxas has no memory because Sora became heartless by the special way. Generally, Nobodies and the origin of Nobodies can never exist at the same time. But Sora and Roxas do. Why?

If you get interested in this story, play KIGDOM HEARTS, or read their novels.
This movie is my really favorite movie.