The fonts that are present when using Japanese as the main language are inconsistent. When it comes to numbers (like stack counts) it seems to be in an arial like font when in the hotbar, or an outside object (such as a chest or crafting table), but when in just your inventory it is in the classic Mojangles font. On top of this the coordinates and XP are in the arial-esk font and are off kilter because of it. When it comes to characters it is clear that there is a Mojangles font but it only seems to be used on items (in inventory or chests but not as a hotbar preview). This font is not present in text chat, on the coordinates, or in title commands. I know the font exists because when I use a title command with someone else playing in English, it uses the Mojangles font. If this was intentional I would expect consistency, but as it is not, I am considering it a bug.