  We propose to search for a boosted dark matter (DM) particle from
astrophysical sources using an emulsion detector in deep underground
facilities. We further propose using high-$Z$ material such as the lead for a
larger DM-nucleus coherent scattering cross section above a threshold. The
boosted DM will scatter into an excited DM. While the nuclear recoil energy is
not detected, the decay products from the excited DM can be recorded by the
proposed detector. Backgrounds such as the high energy solar neutrinos can be
controlled by the reconstructed track topology. The proposed detector has the
potential to find a boosted DM in the sub-GeV mass region, and in certain
parameter space, an observation can be made while there is no sensitivity in
other large-volume detectors such as Super-K.
