I learned English from adulthood only in Japan .Now I think I got to be able to speak so sufficiently as to express what I am thinking and what I want to say in English. So I believe We Japanese can be English speakers without special method. Of course , I want to be more fluent and skillful learning more.There is no goal in studying something. However, there was certainly a moment when I felt I could show what I want to say in English.
Leaning English only in Japan from adulthood is very tough.Every day, I practiced interpreting Japanese sentence into English and repeated it.It is like boot camp. Translating into English itself is hard training.It is also tough to rearrange Japanese sentence I want to speak in my head so that I can translate the sentence easily into English.I felt my national language is as important as other language I wanted to learn because I think in Japanese and build the sentence in Japanese.
Raising the speed of interpreting and outputting are challenging too. I interpreted a number of Japanese sentence.I did it with Japanese newspaper and novels and then talked to myself in English.I think those were good training ways to build up my skill.Slowly but certainly I developed my skill.
My strong point is that I know what those who are learning English only in Japan want and troubles they also have because I was just one of them, or I am.