Mike Cash said:1. A degree in English is not only not required in order to teach English, it is actually rather rare among English teachers.
2. There is no predetermined length to "however long" one must reside in Japan in order to be able to seek citizenship. And it isn't unusual for granting of citizenship to take a year or two from the time of application.
3. Merely residing/working in Japan isn't generally sufficient to put one on a track toward granting of citizenship.
4. How in the hell you think anyone is going to do all that crap before the age of 27 is beyond me.
You're quite right, that's why I said near impossible - but it isn't IMpossible.