The Internet is international. You are as likely to get uploads from people in Japan as you are from people in the United States. Different countries use different character systems and your upload component has to be able to handle both Japanese and English characters.
ABCUpload handles all this for you transparently via Unicode support. For example a visitor uploads a file with a Japanese name - all the file details will arrive intact. You can decide whether you want to convert the name into something more URL friendly or if you want to use the Japanese name (or a derivation of it).
Of course ABCUpload isn't specific to Japanese. Unicode covers every character system in the world.