  We perform a general-relativistic neutrino-radiation magnetohydrodynamic
simulation of a one second-long binary neutron star merger on Japanese
supercomputer Fugaku using about $72$ million CPU hours with $20,736$ CPUs. We
consider an asymmetric binary neutron star merger with masses of $1.2$ and
$1.5M_\odot$ and a `soft' equation of state SFHo. It results in a short-lived
remnant with the lifetime of $\approx 0.017$\,s, and subsequent massive torus
formation with the mass of $\approx 0.05M_\odot$ after the remnant collapses to
a black hole. For the first time, we confirm that after the dynamical mass
ejection, which drives the fast tail and mildly relativistic components, the
post-merger mass ejection from the massive torus takes place due to the
magnetorotational instability-driven turbulent viscosity and the two ejecta
components are seen in the distributions of the electron fraction and velocity
with distinct features.
