  We propose a possibility of ultrarelativistic electromagnetic counterparts to
gravitational waves from binary neutron star mergers at nearly all the viewing
angles. Our proposed mechanism relies on the merger-shock propagation
accelerating a smaller mass in the outer parts of the neutron star crust to a
larger Lorentz factor $\Gamma$ with smaller energy $\sim 10^{47} \Gamma^{-1}$
erg. This mechanism is difficult to resolve by current 3D numerical
simulations. The outflows emit synchrotron flares for seconds to days by
shocking the ambient medium. Ultrarelativistic flares shine at an early time
and in high-energy bands, potentially detectable by current X-ray to radio
instruments, such as Swift XRT and Pan-STARRS, and even in low ambient density
$\sim 10^{-2}$ cm$^{-3}$ by EVLA. The flares probe the merger position and
time, and the merger types as black hole--neutron star outflows would be
non-/mildly relativistic.
