German as main language + english and japanese

Question

Hey @all (& a happy new year),

I am currently facing the challenge of including 3 languages and 2 different writing systems in one document. These are: German as main language, English as an additional language and Japanese as the third language. When it comes to Japanese, there are some additional requirements, however since I already fail at the basics, I will try to ask for everything in an order. 1) I noticed there is a package called "LuatexJa" which is supposed to help when it comes to mainly japanese documents. However, for me, the ratio will always be German > Japanese. I tried using it, but it kind of broke my formatting for the German text parts. 2) I would like to use a specific font (Yu Mincho Light), but since I didn't know how to apply it (I checked the LuatexJa" manual, but it didn't work for me using Overleaf), I stuck with the standard one for now

Here is an example (the text does not make sense semantically - it just serves as a visual example) :

Thank you so much in advance!

 \documentclass[12pt,a4paper,headings=standardclasses,numbers=noenddot]{scrreprt}
%\usepackage{showframe}
\usepackage[left=2.50cm, right=2.50cm, top=2.50cm, bottom=2.00cm]{geometry}
\usepackage[onehalfspacing]{setspace}
\usepackage[main=ngerman, english]{babel}
\usepackage[babel, german=quotes]{csquotes}
\usepackage[ngerman]{isodate}
\usepackage[ngerman]{datetime}
\usepackage{libertine}
\usepackage{libertinust1math}
%   Alternative Times
%   \usepackage{times}
%   \fontfamily{ptm}\selectfont
\usepackage[yu-win10]{luatexja-fontspec}
\setmainfont{Linux Libertine O}
\setmainjfont{IPAexMincho}
\usepackage{luatexja-ruby}
%----------------------------------------------------------------------------
\begin{document}
\chapter*{Abstract}
Cho unterbreitet in dem Sammelband „Routledge Handbook of East Asian Popular Culture“, der 2017 von Kōichi \textsc{Iwabuchi} herausgegeben wurde, einen interessanten Vorschlag zum Verständnis der asiatischen Populärkultur. Diese fasst er als „Mélange of iterations“ auf und stellt damit der für ihn bislang nur westlich-zentrierten Forschung einen asiatischen Ursprung und Blickwinkel gegenüber. こんにちは、\ltjruby[]{皆|様}{みな|さま}！
\end{document}

Answer 1

What I see is that the quotation marks are badly treated. Skimming in the documentation I found the following:

\documentclass[12pt,a4paper,headings=standardclasses,numbers=noenddot]{scrreprt}
%\usepackage{showframe}
\usepackage[left=2.50cm, right=2.50cm, top=2.50cm, bottom=2.00cm]{geometry}
\usepackage[onehalfspacing]{setspace}
\usepackage[main=ngerman, english]{babel}
\usepackage[babel, german=quotes]{csquotes}
\usepackage[ngerman]{isodate}
\usepackage[ngerman]{datetime}
\usepackage{libertine}
\usepackage{libertinust1math}

\usepackage{luatexja}
\usepackage[yu-win10]{luatexja-fontspec}
\usepackage{luatexja-ruby}

\setmainfont{Linux Libertine O}
\setmainjfont{IPAexMincho}

\ltjsetparameter{jacharrange={-3}} % <--- punctuation is Latin

\begin{document}

\chapter*{Abstract}

Cho unterbreitet in dem Sammelband „\foreignlanguage{english}{Routledge 
Handbook of East Asian Popular Culture}“, der 2017 von 
Kōichi \textsc{Iwabuchi} herausgegeben wurde, einen interessanten 
Vorschlag zum Verständnis der asiatischen Populärkultur. Diese fasst er 
als „\foreignlanguage{english}{Mélange of iterations}“ auf und stellt 
damit der für ihn bislang nur westlich-zentrierten Forschung einen 
asiatischen Ursprung und Blickwinkel gegenüber. 
こんにちは、\ltjruby[]{皆|様}{みな|さま}！

\end{document}