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.
Various studies have been carried out on Satoshi with no results, I believe Satoshi is a real person, it's just that his name is not real, if Satoshi's name is registered as a real name, it's easy for people to investigate.
I'm sure Satoshi, is still on this forum, only the name of the account he manages is unknown, what is clear is that Satoshi has done his best for the whole world in terms of digital currency, namely Bitcoin.