  We present a weak lensing cluster search using Hyper Suprime-Cam Subaru
Strategic Program (HSC survey) first-year data. We pay special attention to the
dilution effect of cluster member and foreground galaxies on weak lensing
signals from clusters of galaxies; we adopt the globally normalized weak
lensing estimator which is least affected by cluster member galaxies, and we
select source galaxies by using photometric redshift information to mitigate
the effect of foreground galaxies. We produce six samples of source galaxies
with different low-$z$ galaxy cuts, construct weak lensing mass maps for each
of the source sample, and search for high peaks in the mass maps that cover an
effective survey area of $\sim$120 deg$^2$. We combine six catalogs of high
peaks into a sample of cluster candidates which contains 124 high peaks with
signal-to-noise ratios greater than five. We cross-match the peak sample with
the public optical cluster catalog constructed from the same HSC survey data to
identify cluster counterparts of the peaks. We find that 107 out of 124 peaks
have matched clusters within 5 arcmin from peak positions. Among them, we
define a sub-sample of 64 secure clusters that we use to examine dilution
effects on our weak lensing cluster search. We find that source samples with
the low-$z$ galaxy cuts mitigate the dilution effect on weak lensing signals of
high-$z$ clusters ($z > 0.3$), and thus combining multiple peak catalogs from
different source samples improves the efficiency of weak lensing cluster
searches.
