In my many years teaching English in Japan I have come to understand the reasons why japanese students have a hard time developing English speaking skills, I think.
One of the reasons is that they spend a long time writing and reading English. As a result they can write beautifully and also have excellent Reading Comprehension.
American students on the other hand spend much time talking, expressing ideas and opinions about almost any topic. Some become great speakers but too many have poor writing skills, spell badly, have poor vocabulary and have a hard time understanding what they read. At College there are remedial classes such as English 1 and 2, English Writing, etc. to help students with the language; when I was at Santa Monica College, most of the students attending these classes were foreigners, most natives did not take these courses, after all they were natives.
How to develop fluency:
I believe japanese students already have a very good base to improve their speaking skills, Focus should be on the student speaking. It is the student who should spend most of his time speaking in class, not the teacher.
Firstly try to speak in blocks of sentences do not speak word by word, avoid gaps or long pauses.
Secondly, try singing your favorite English song and imitate sounds, rhythm, intonations, pause and stress.
That is the first step, next avoid teachers that spend too much time talking about themselves, overcorrect you or get angry because you can not pronounce well.
Choose a professional teacher not just any native speaker of English. This is very important, choose a teacher that you can feel cares about your progress and will help you achieve your goals.
Just chatting in English is not going to help you either, you need to be shown direction, taught how to express your ideas, reasoning and thinking using standard correct English, so that anyone will understand you.
Failure to communicate in Business and in Academic life using English is one of the greatest problems facing this new generation, we need to talk.
Please try to put these points into practice and walk towards your goal slowly but with self-confidence with the helping hand of your favorite teacher, and most of all you will enjoy your learning.
My best wishes to you, enjoy your journey. English is a very simple language yet in its simplicity lies its beauty.