FromSoftware released today the official Japanese language package for the PC (Steam) version Dark Souls: Prepare to Die Edition. You can selected the language package even if you don’t live in Japan. According to the official Steam update blog you have to pay attention about this:
“if you were to choose “Japanese” as your ingame language, all mods currently added to your game will be disabled as they will not be compatible when the update is live.”
If waited until now to buy the game because of the Japanese translation now you can grab it.
— フロム・ソフトウェア／公式 (@fromsoftware_pr) January 6, 2017