\begin{overpic}[width=0.49\textwidth]{tour4}
\put(1,74){\colorbox{white}{(\sublabel{tour4}) \href{http://dream.misasa.okayama-u.ac.jp/?q=20210114061332-615711}{tour4}}}
%%(\subref{tour4}) \href{tour4}
\color{red}
\end{overpic}