Q:

Is there any method available to automatically show the ruby when writing sentences with Japanese Kanji?

I want to write a note for my study on Japanese Language with LaTeX. So far I have to write the ruby (furigana) for each Kanji manually such as \ruby{天}{てん}. It seems to be tedious and makes my input file no longer "natural". 
What I want to have is to let the computer (LaTeX) automatically provide the ruby for every single Kanji character (if possible) or a set of Kanji characters (for compound words).
Is there any method available to automatically show the ruby when writing sentences with Japanese Kanji in LaTeX?
\documentclass{article}
\usepackage{ruby}
\begin{document}
Is \ruby{this}{MWE} really needed? I don't think so.
\end{document}

A:

It is not as easy as you may think.  For a text processor to do a reasonable job at detecting word boundaries in Japanese you need to do morphological analysis on it.  You can then look up each word in a dictionary and add the ruby for each kanji, but doing that automatically will probably introduce errors too.
Anyway, it would be a rather involved project to do that in TeX.  Any reasonable attempt would of course use existing tools.  A very quick Google search yields for example this site that offers tools in Python (what you would need here is their jTokenize function).  There a several other tools.  This page from Microsoft Research, about their own tools, explains the general issue of natural language processing for Japanese.
In other words: it’s practically a research-level project.

