I tried that, and the words do appear in the df file, and the entries look right as far as I can tell (based on what I see in the dictutil documentation). I got responses from both the Pyglossary developer and the dictutil developer on one of the issues I opened and it sounds like Japanese is not fully supported by Pyglossary/dictutil.
https://github.com/ilius/pyglossary/issues/292
So, I guess I have to wait. In case anyone comes across this thread later and wants to see the status of these issues, here's the other one I opened on dictutil:
https://github.com/pgaskin/dictutil/issues/16