You can download the demo directly from Namco Bandai right now. The multiplayer demo has four playable characters: Naruto, Kakashi, Pain, and Konan. Set up fights against the computer or a friend. The demo includes ad-hoc wireless play plus three maps: Village Hidden in the Leaves, Akatsuki Hideout, and Cliff of the Morning Mist.
Get the demo here. Naruto Shippuden: Ultimate Ninja Heroes 3 hits North America on May 11 and Europe a few days later on May 14.