Having done that translation a few years ago, our Japanese contact has just recently discovered my unschooling site and is putting parts of it into a blog with my permission, encouragement and gratitude.
A page with some of the text from my main unschooling page is here, and a translation of some of what is in the
Homeschooling Book of Answers is here. (backup copy)
articles in other languages (Chinese, Spanish, French, German, Italian, maybe more)