プリアンブルに

\documentclass[a4paper,12pt]{jarticle}
\setlength{\textwidth}{18cm}
\setlength{\oddsidemargin}{-1cm}
\setlength{\textheight}{25cm}
\setlength{\headsep}{-0.2cm}
\setlength{\headheight}{-0.8cm}
\pagestyle{empty}
\newcommand{\qed}{\hbox{\rule{6pt}{6pt}}}
\newcommand{\qqed}{\hbox{\rule{4pt}{5pt}}}
\usepackage{multicol}
\usepackage{amsmath,amssymb}
     \usepackage{plext}%
     \usepackage{fancybox}%
     \usepackage{ulem}%
     \usepackage{makeidx}%
     \usepackage{hako}%
     \usepackage[pzd]{emathFx}%
     \usepackage{emathEy}%
     \usepackage{emathMw}%
     \usepackage{emathThm}%
     \usepackage{emathCap}%
     \usepackage{emathAe}%
     \usepackage{emathR}%
     \usepackage{emathP}%
     \usepackage{showexample}%
     \usepackage{cases}%

と入力してあるんですが、\HenKoを使うと

! Undefined control sequence.
<argument> \xmin 
                 \xunitlength 
l.129 ...toption={(-2mm,0)},henkoH=2.0ex>\J\I{4cm}
                                                  %
The control sequence at the end of the top line
of your error message was never \def'ed. If you have
misspelled it (e.g., `\hobx'), type `I' and the correct
spelling (e.g., `I\hbox'). Otherwise just continue,
and I'll forget about whatever was undefined.

と出てしまうのは何が原因でしょうか。

▼関連発言
│
└◆8351:質問です [Naoki] 09/21 11:49
　└◆8352:Re:質問です [tDB] 09/21 11:57
　　└◆8353:Re[2]:質問です [Naoki] 09/21 12:00<-last