Now, I've never even seen Naruto, but as an anime fan, I know how important it is to get subtitled Japanese dubs to avoid bleeding out of your ears from the often subpar English translations and dub work. Sure, they're getting better all the time, but purists prefer the original language if possible. Well, when Naruto: Rise Of A Ninja was released for the Xbox 360, Ubisoft promised a free download via Xbox Live that would let you play with Japanese voices, and today they have delivered.
The official Japanese Naruto voice cast is now available via Xbox Live Marketplace as a free download (only Silver account required!). Just boot up your game, and select XboxLive Marketplace from the main menu, download the Japanese voice package, then activate it in the options and enjoy!
(Now, why this wasn't available as an option at the game's launch is a mystery to me... but better late than never, right?)