Your ability to get a job at a bank/hedge fund will depend on your japanese language ability. Fortuntely for you, sales and trading jobs tend to be less demanding in terms of language, but that just means you will need business level fluency rather than native level.
I know it's a stretch for you, but if you're in the states in November, the Boston Career Forum is hands down the best place to interview finance jobs in Japan. All the big US banks send reps from their Japanese branches.
CFN | Boston Career Forum 2008
There is a similar event in London, which would be more doable for you, but it has already passed for this year, so you'd have to wait until next summer to have a crack at that. I'm not sure if it's as large as the Boston one though...
CFN | London Career Forum 2008