Re: Do I need Japanese to practice in Japan?
you will probably get better advice from our Tokyo residents in the forum.
Tokyo is probably a good city for you as many organizaitions have their honbu dojo in Tokyo, which are prepared to host foreign visitors and/or have international members.
One idea: look at the dojo-search section here on aikiweb and look for dojo in Tokyo. If they have an English web site, you might have good chances. If they just have an email address, you can ask by mail.
But whatever you do - work hard on your Japanese. In the beginning it might just be seen as showing good-will, but as soon as you can exchange simple sentences, about weather, general sports or even the last training, everything else will work much easier.
Have much fun