Bitcoin is in many main languages but not Japanese. Why would the guy who created it not make it in his own language? Don't you find it suspicious MtGox is in Japan?
Also the project really isn't a success. A lot of progress still has to be made. Security is still an issue along with sites still growing. Anyone ever even talk to him? I'm not saying he isn't real I'm just putting this out there.
Who thought you that satoshi uses his own language or different language from Him? and besides what do you care if satoshi is real or not? isn't better that what you must be thankful is that the man provide you something that is really worth to be thankful?
imagine there is a Bitcoin and now tons of cryptocurrencies that helps us with our own lives and our transactions here and there.