\documentclass{jsarticle}
\usepackage{multirow,eepic}

\makeatletter
\def\senbun#1(#2)#3({\@senbun(#2)(}
\def\@senbun(#1,#2)(#3,#4){%
   \@tempdima#1\p@ \advance\@tempdima#3\p@
   \divide\@tempdima\tw@
   \@tempdimb#2\p@ \advance\@tempdimb#4\p@
   \divide\@tempdimb\tw@
   \edef\@senbun@temp{\noexpand\qbezier(#1,#2)%
      (\strip@pt\@tempdima,\strip@pt\@tempdimb)(#3,#4)}%
   \@senbun@temp}
\makeatother

\begin{document}

\begin{tabular}{|c|c|}
\hline
左&\senbun(0,9)(20,-5)\\ \hline
\senbun(0,-5)(20,9)&下 \\
\hline
\end{tabular}

\begin{tabular}{|c|c|}
\hline
左&\senbun(0,11)(21,-5)\\ \hline
\senbun(0,-5)(21,11)&下\\
\hline
\end{tabular}

\begin{tabular}{|c|c|}
\hline
左ああ&\senbun(0,11)(67,-5)\\ \hline
\senbun(0,-5)(39,11)&あああああ下\\
\hline
\end{tabular}

{\renewcommand{\arraystretch}{1.1}
\begin{tabular}{|c|ccc|c|c|}
\hline
 0 & 1 & 2 & 3 & 4 & 5  \\
\hline
 a & 2 & 3 & 4 & 5 & 6  \\
\cline{2-6}
 c & 3 & 4 & 5 & 6 & 7  \\
\hline
   & 4 & & &\multirow{3}{*}{\senbun(-8,16)(8.5,-36)} & \\
 d & 5 & & & & \\
   & 6 & & & & \\
\cline{2-6}
 e &   & & & \senbun(0,12)(17,-8) &  \\[3pt]
\hline
\end{tabular}
}

\end{document}
