  We study the $S$-wave $D\bar{D}^*(I=0)$ scattering at four different pion
masses $m_\pi$ ranging from 250 MeV to 417 MeV from $N_f=2$ lattice QCD. A
bound state near the $D\bar{D}^*$ threshold likely exists even after
considering the possible left-hand cut effect due to the one pion exchange
interaction. At $m_\pi\approx 417$ MeV where the effective range expansion is
valid, the compositeness of the bound state is $X\approx 1$ and indicates a
predominant $D\bar{D}^*$ component. This state may correspond to $X(3872)$. On
the other hand, our results of the finite volume energies also hint at the
existence of a $1^{++}$ resonance below 4.0 GeV with a width around 60 MeV.
