@jonsmth
You say that like I don't know the difference between those different words.
Yes, there can be a number of ways to say "I" and "brother" with a myriad of ways to denote respect, BUT the problem is there are very clear and distinct english equivalents to every single instance that was presented here.
Okaa-sama = Mother (instead of Mom or Ma)
Imouto = little sister (instead of kid sister or sis)
Origatou gozaimasu = Thank you very much (instead of a plain thanks)
Ojii-chan = Grandpa (instead of Grand Father or even Gramps)
Obaa-chan = Grandma (instead of Grand Mother)
Again, I would be willing to give you that there are nuances that the author tried to convey through their language, but not a single instance here is a time where there is no english equivalent that would deliver the exact same emotion and impact. What the translator did was one of two things: be lazy or simply decide that untranslated japanese words fit in the setting of a faux-european country. Either of these choices are incredibly dumb. If it
was a good choice, then professional localization companies would be doing this too. Which they clearly do not.