\documentclass{jarticle}
\usepackage{enumerate}

\def\iroh{色は匂へど散りぬるを我が世誰ぞつねならむ
有為の奥山今日越えて浅き夢見じ酔ひもせず}

\newcommand\tightlist{\setlength\itemsep{0pt}\setlength\parsep{0pt}}
\newenvironment{myitemize}{\begin{itemize}\tightlist}{\end{itemize}}

\begin{document}

\begin{enumerate}[{Year} 1:\enspace]
\tightlist
\item \begin{myitemize}
\item \iroh
\item \iroh
\item \iroh
\end{myitemize}
\item \begin{myitemize}
\item \iroh
\item \iroh
\item \iroh
\end{myitemize}
\item \begin{myitemize}
\item \iroh
\item \iroh
\item \iroh
\end{myitemize}
\end{enumerate}

\dotfill

\end{document}
