+As noted in Introduction, a JFM has measurements of characters and
+glues/kerns that are automatically inserted for Japanese
+typesetting. The structure of JFM will be described in the next
+subsection. At the calling of \verb+\jfont+ primitive, you must specify
+which JFM will be used for this font by the following keys:
+
+\begin{list}{}{\def\makelabel{\ttfamily}\def\{{\char`\{}\def\}{\char`\}}}
+\item[jfm=<name>]
+Specify the name of JFM. A file named \texttt{jfm-<name>.lua} will be searched and/or loaded.
+
+The followings are JFMs shipped with Lua\TeX-ja:
+\begin{description}
+\item[\tt jfm-ujis.lua] A standard JFM in Lua\TeX-ja. This JFM is
+ based on \verb+upnmlminr-h.tfm+, a metric for UTF/OTF package that
+ is used in \upTeX. When you use \texttt{luatexja-otf.sty}, please use this JFM.
+\item[\tt jfm-jis.lua] A counterpart for \verb+jis.tfm+, `JIS font
+ metric' which is widely used in \pTeX. A major difference of
+ \texttt{jfm-ujis.lua} and this \texttt{jfm-jis.lua} is that
+ most haracters under \texttt{jfm-ujis.lua} are square-shaped,
+ while that under \texttt{jfm-jis.lua} are horizontal
+ rectangles.
+
+\item[\tt jfm-min.lua] A counterpart for \verb+min10.tfm+, which is one
+ of the default Japanese font metric shipped with \pTeX. There
+ are notable difference between this JFM and other 2~JFMs, as
+ showed below:
+
+何かいい例.単純に「min10にはバグあり」ではなく,プロポーショナルな側面も見せたいよね
+(乙部さんのmin10.pdfの例を使う?)
+\end{description}
+
+\item[jfmvar=<string>] ...
+\end{list}
+