Instructions
Turn on the PSP with the "Naruto Shippuden: Accel 3" game inside. Load the game to the main menu screen and select a game to start. Press the top button to start a new game, or press the bottom button to load a saved game.
Load a game or start a new game and get to the game selection menu. This is a menu that takes up the right half of the screen with rotating options allowing you to choose "story" or "versus" modes. The fourth menu item is "options."
Select the "Option" item from the menu, and locate the "Language" options. The Japanese version of this game does not have a language options section in the menu, and the English version only changes the spoken dialogue from English to Japanese or vice versa, so the menu items should still be in English.
Change the language options to English. Press the corresponding buttons, as guided by the on-screen instructions, to select the language and exit out of the menu. The language change should be immediate.