An input method is an operating system component or program that allows users to enter characters and symbols not found on their input device. For instance, on the computer, this allows the user of ‘Western’ keyboards to input Chinese, Japanese, Korean and Indic characters. On many hand-held devices, such as mobile phones, it enables using the numeric keypad to enter Latin alphabet characters.
Unity provides IME support, which means that you can write non-ASCII characters in all your graphical user interfaces. This Input Method is fully integrated with the engine so you do not need to do anything to activate it. In order to test it, just change your keyboard language to a non-ASCII language (e.g. Japanese) and just start writing your interface.
For more info and optimization when writting non-ASCII characters, check the character option in the font properties.
This feature is not supported on Android devices yet.