Even in a best-case scenario, you'll be lucky to get anything at all. Even assuming there is a successful lawsuit, and after all of the assets have been divided up, and after the lawyers have taken their fees, in 10 years maybe you'll end up with $20. Maybe.

I doubt it. IANAL, but it must depend on how much money you lost.

Have you ever been part of a class action?

I was invited to one last week, actually, but don't know if I'll get involved.

I'm not even sure if there is such a thing in japan. In my perception class action lawsuits always have been a us-anomaly.

Against whom? From the little I know about this case, it seems MtGox, Inc. (or whatever it's called) will be liquidated once the mess is sorted out.

If you file against MtGox (class-action or otherwise) right now, you could be listed as a creditor in their bankruptcy, and would benefit greatly from said liquidation.

Not all jurisdictions allow filing against a bankrupt entity, and considering that Japanese law is heavily influenced by German law, I doubt it's possible in Japan. I can't find any easily accessible English language literature on it, though.