Are there martial arts academies in Japan?
Yes, there are many martial arts schools in Japan. There are even Mutai, Kung Fu, and other imported martial Arts schools now. The times have changed and most dojos will allow you to join even if you are a foreigner. A friend had been here for over 20 years from England studying Kendo and is a 6 dan in Kendo and a 3 dan in Iyaido. It will help very much if you have a recommendation from a school outside of Japan but if not, a serious desire to learn will get you in. The mainstream martial arts in Japan are Kendo, Karate, Aikido, and Judo.