As everyone said, if possible, try and avoid the Japanese banks.

I found Mizuho was particularly difficult to deal with unless you're very proficient in Japanese because all of the documentation is in Japanese, they require you fill out the forms yourself in Japanese, and you'll need a hanko.

Citi JP was okay to deal with, but I don't think they'll work for your purposes since they aren't closely linked with Citi US and also have a minimum balance requirement (last year it was Y1,000,000 and I imagine it's still the same).

Alex