But it's not translated and it's not an easy thing to do, because the game is huge and it's still getting updates (fixes) frequently so it's not worth doing the translation.
Mtool extracts text to be translated which then can be applied to the game on the fly but it only works with the tool and it's otherwise useless (unless somebody can write some script to search and replace text extracted from the game's files with mtool's json translation file). You don't worry about bugs caused by translation and about game updates - new text will simply appear untranslated.
Yeah I ran into that before too. When in gallery hit the "c" key and you'll get a menu pop up, select whatever it shows on the 3rd line down, mine says "Tachie". Then you can edit all characters standing images and also enable/disable options for how each character reacts to / says during certain events. They also take effect inside your saves as well so be careful with that.
Can mtool somehow translate the menu or is that kinda that weird thing that it the menu buttons are "drawn" so it can't translate the text as there is technically no text?