Forget the plugin idea. You need a native Japanese speaker to check it. According to Diane Burns who has an excellent video on creating multilingual publications and who specializes in publications for the Asian market, the Japanese have a very complex system of composition. I highly recommend her video on Lynda.com:
Also, make sure you are using Adobe World-Ready Paragraph Composer. I had once an issue with Hindi text and that was the problem.
Unlike InDesign, English-language Adobe Illustrator, has the ability to use kinsoku line-breaking rules for Japanese, so you can find an introduction to the subject in English in AI's documentation. Such CJK features aren't available in western-language versions of InDesign unless you install Harbs' World Tools Pro, which includes an interface for adjusting kinsoku settings.