  We investigate the emergence of hyperons in black-hole-forming failed
supernovae, which are caused by the dynamical collapse of nonrotating massive
stars. We perform neutrino-radiation hydrodynamical simulations in general
relativity adopting realistic hyperonic equation-of-state (EOS). Attractive and
repulsive cases are examined for the potential of \Sigma\ hyperons. Since
hyperons soften the EOS, they shorten the time interval from the bounce to
black hole formation, which corresponds to the duration of neutrino emission.
This effect is larger for the attractive case than the repulsive case because
\Sigma\ hyperons appear more easily. In addition, we investigate the impacts of
pions to find that they also promotes the recollapse towards the black hole
formation.
