I agree, Simple and Clean was a fantastic song. In fact, it was because of that song, I became a Utada fan. So I think it's one of her best songs she has ever sung. It's probably still my top favorite. It would be nice to have Simple and Clean on the Exodus album, but it definitely wouldn't match. The whole album seemed to have a theme to it. The songs on the album, from what I think, go well together. Simple and Clean would've stood out to much. Plus it was used in Kingdom Hearts and I think Utada wanted it to be seperated from the music on her Exodus album.