  We present results from a set of simulations designed to constrain the weak
lensing shear calibration for the Hyper Suprime-Cam (HSC) survey. These
simulations include HSC observing conditions and galaxy images from the Hubble
Space Telescope (HST), with fully realistic galaxy morphologies and the impact
of nearby galaxies included. We find that the inclusion of nearby galaxies in
the images is critical to reproducing the observed distributions of galaxy
sizes and magnitudes, due to the non-negligible fraction of unrecognized blends
in ground-based data, even with the excellent typical seeing of the HSC survey
(0.58" in the $i$-band). Using these simulations, we detect and remove the
impact of selection biases due to the correlation of weights and the quantities
used to define the sample (S/N and apparent size) with the lensing shear. We
quantify and remove galaxy property-dependent multiplicative and additive shear
biases that are intrinsic to our shear estimation method, including a $\sim 10$
per cent-level multiplicative bias due to the impact of nearby galaxies and
unrecognized blends. Finally, we check the sensitivity of our shear calibration
estimates to other cuts made on the simulated samples, and find that the
changes in shear calibration are well within the requirements for HSC weak
lensing analysis. Overall, the simulations suggest that the weak lensing
multiplicative biases in the first-year HSC shear catalog are controlled at the
1 per cent level.
