This language pack translate most of Minecraft into Rōmaji (Japanese with latin characters)
Exceptions are items, tools and some parts of the menu (Which I could not seem to find to change.)
Includes splashes (Yellow text in main menu), and achievements.
Please read the main topic above again. The items are an exception to the translation. I figured, because they are English nouns (And English nouns are not translated when speaking) that there wouldn't be a need to translating them.