Seems like this is the start of the fantasy Japan arc (there's always one everywhere), considering the cover of volume 9. I guess this will be Kenzaburo's/ Grace's time to shine even more, Kenzaburo's using his actual Japanese knowledge and manners and Grace participating in some diplomacy as the fiancee of the crown prince and prospective future queen.
While it's weird seeing East-Asian inspired characters speak old english and french, I think you made a good choice using those langauges - after all this is a translation into english, so picking languages that are slightly different, but still familiar to Westerners is a good decision.
Thanks for the translation.