  The cosmic microwave background (CMB) contains an anomalous cold spot with a
surrounding hot ring, known as the Cold Spot. Inoue & Silk (2006) proposed that
this feature could be explained by postulating a supervoid: if such a large
underdense region exists, then the growth of matter perturbing around the spot
might differ from the average value in the Universe and the differences might
affect weak lensing analysis of peak statistics. To investigate environmental
effects on halo number count and peak statistics, we used a publicly available
ray-tracing simulation for a box size of 2250$h^{-1}$Mpc on a side (Takahashi
et al. 2017). We found that the number counts for massive haloes toward the
largest underdense region in the simulation decreases and the corresponding
significance of the difference, based on a cosmic average, is $\geq3\sigma$. On
the basis of the results of peak statistics analysis, the number of high peaks
decreases with the decrement of massive haloes, but the number of low peaks
increases with the lack of matter in the line of sight. The highest
significance of the decrement in peak counts in large underdense regions is
$5\sigma$ in the total signal-to-noise ratio. Our result implies that
environmental effects on halo abundance and weak lensing peak statistic can be
used to probe the presence and properties of supervoids.
