% -*- coding:euc-jp; -*-

\documentclass[onecolumn,12pt]{book}

\usepackage{nruby}

\begin{document}

日本語を書こう…。

\vskip1cm

With furigana (requires nruby-package, included above):

\useruby
@日(に)@本(ほん)@語(ご)を@書(か)こう…。
\nouseruby

Other international characters, which are usually unavailable in euc-jp can be
accessed with their \TeX escape sequences: \"u \"a \"O etc.

\end{document}