Who is the anonymous japanese? As this is a thread about MtGox, which is a Japanese company, maybe you refer to the owner? FYI: he is not anonymous and he is not japanese. He is French and his name is Mark Karpeles.
What is public knowledge about this guy? There is no Wikipedia article or the like...
Is he a weirdo?
Well, there aren't Wikipedia articles of a lot of CEOs. I'd say that 90% of CEOs in the world don't have a Wikipedia entry for them. But there is a Wikipedia entry for MtGox.
MtGox is a fully registered company, scrutinized by law, with a large history of legitimacy. That's why is such a pain to comply with all their documents requirements, because they are ultra legit.
Public knowledge about Karpeles? You have to be new to ask for that. There's a lot of public info about him. Start checking here:
http://lmgtfy.com/?q=Mark+Karpeles+mtgox