  We study the microrheology of active suspensions through direct hydrodynamic
simulations using model pusher-like microswimmers. We demonstrate that the
friction coefficient of a probe particle is notably reduced by hydrodynamic
interactions (HIs) among a moving probe and the swimmers. When a swimmer
approaches a probe from the rear (front) side, the repulsive HIs between them
are weakened (intensified), which results in a slight front rear asymmetry in
swimmer orientation distribution around the probe, creating a significant
additional net driving force acting on the probe from the rear side. The
present drag-reduction mechanism qualitatively differs from that of the
viscosity-reduction observed in sheared bulk systems and depends on probing
details. This study provides insights into our fundamental knowledge of
hydrodynamic effects in active suspensions and serves as a practical example
illuminating distinctions between micro- and macrorheology measurements.
