I'm looking for the Japanese remix to the song simple and clean from kingdom hearts.

Already checked galabida.

It's the one about 2 & 1/2 minutes in length.

Here, follow this hyperlink:
http://www.kingdomhearts3.net/kh-ost-complete/remixes/
Here you can download the entire soundtrack, and the song you're looking for is the very last one in the soundtrack.

It's got the english version I'm looking for but no.

http://lanena3s4.imeem.com/music/rQztTJp2/utada_hikaru_simple_and_clean_japanese/

You need to register in order to hear this but this is the exact one I'm looking for.

It actually is the one. You have to go down to the track list and look at the very last song, the last bonus track, and that one is the Japanese version. I downloaded it, but I'm having a little trouble compressing it, but I know it is the one you're looking for. I also spent a very long time looking for it, and when I found it I was relieved. Its name is Hikari (PLANITb Remix [Full]) [BONUS TRACK], if that'll help

Okay. By Japanese remix, do you mean simply the Japanese version, or the remixed version (the PLANiTb mix?)

Just for the record, the Japanese song is the original one, and the English one was made afterwards, to go with the English game.

This the 2:31-long, Japanese, PLANITb mix (I think this is the one you mean.): http://www.sendspace.com/file/macrn1 / http://rapidshare.com/files/72816156/103_Hikari_-PLANITb_Remix-__Short_Edit_.mp3.html

Win.