Hi GMATT73,
I am thinking about Hitotsubashi (Public university) and Waseda (Private university) next year.
These 2 universities have a very good reputation IN Japan. As a consequence, you never see them mentioned in international rankings such as Business Week, FT, ......
Because of no AACSB maybe....certainly (!)
The other universities you named are good too.
I also do confirm Hitotsubashi and Waseda require GMAT and TOEFL. I went to HITOTSUBASHI ICS last month and the score for GMAT should be around 650 to avoid disappointment

and 600 for TOEFL.
Waseda is quite same but, as a foreign applicant, I have to show motivation writing more essays (almost double !!).
I did not take JLPT 1 because my japanese level is farrrr from being bilingual.
That's why I looked for a MBA taught in english. As soon as I know I am accepted (during 1st semester 2007), I will learn seriously japanese in order the following semester (courses start in September or October).