JimmySeal said:
Namely, a book broken into cumulative lessons with a reading sample, an explanation of grammar points (explained in Japanese), and some vocabulary. Some other people in my prefecture have said that despite their best searching, they haven't managed to turn up anything like that.
I work for a TESL institute, and I can see if I can come up with some titles next week for you. They are all, unfortunately, in English, to begin with, designed for people who already have a rudimentary understanding of the language. For yourself, you should definitely try to pick up an advanced college grammar textbook (some of my fellow tutors use
The Little Brown Handbook, which will help you understand and teach the grammar English has. You'll be amazed by all of the complicated rules that you unconsciously know by heart, but have no idea how to explain. Grammar's going to be a huge challenge to teach (and for the student to learn). Japanese doesn't have plural nouns or verbs or direct/indirect articles (like "a" and "the").
Get yourself a good English dictionary, and a Japanese-English dictionary for vocabulary (things you probably already own), but make sure they use the English-only dictionary (if their comprehension of English is good enough) for definitions. As they improve, start getting them to read books and articles aloud with you. Also, watch movies with them in English, first with Japanese subtitles, and later, with English subtitles, and eventually, with none at all.
I hope this helps some. Of course, the best way to learn any language is to be immersed in it, but you've got to deal with what you've got. Good luck.