Just try to find something for foreign kids to do in Japan in the summer. There aren't many options, even if your children speak Japanese, as mine do. The most difficult period of all is the five or six weeks after international schools close down but Japanese schools are still in session.
This wasn't an issue when both my kids were in Japanese school, where the summer holiday exists in name alone. The six weeks they call "summer vacation" are peppered with school activities including swimming lessons, review classes and tons of homework.
But now that my older boy attends an international middle school -- it finished June 9 and won't resume until Aug 25 -- we're on our own when it comes to organizing summer fun: There are no school activities, no club meetings, not even a scrap of homework.