  We consider the half-wave equation with mass critical in two dimension
\begin{eqnarray*} \begin{cases} iu_t=Du-|u|u,\,\,\, \\ u(0,x)=u_0(x),
\end{cases} \end{eqnarray*} First, we prove the existence of a family of
traveling solitary waves. We then show the existence of finite-time blowup
solutions with minimal mass $\|u_0\|_2=\|Q\|_2$, where $Q$ is the ground state
solution of equation $DQ+Q=Q^2$.
