Better yet, just put the Japanese with furigana. The u doesn't bother me.
well you speak English, not French as native language
O and OU are 2 totally different sounds in French. I don't know about any other languages that may have similar issues.
OH as some of my Japanese friends write in Romaji would be more acceptable.
Turnbull has decided once for all just to put O. Guess that is the solution when you do not want to take a risk.