  We analyse the M31 halo and its substructure within a projected radius of 120
kpc using a combination of Subaru/HSC NB515 and CFHT/MegaCam g- & i-bands. We
succeed in separating M31's halo stars from foreground contamination with
$\sim$ 90 \% accuracy by using the surface gravity sensitive NB515 filter.
Based on the selected M31 halo stars, we discover three new substructures,
which associate with the Giant Southern Stream (GSS) based on their photometric
metallicity estimates. We also produce the distance and photometric metallicity
estimates for the known substructures. While these quantities for the GSS are
reproduced in our study, we find that the North-Western stream shows a steeper
distance gradient than found in an earlier study, suggesting that it is likely
to have formed in an orbit closer to the Milky Way. For two streams in the
eastern halo (Stream C and D), we identify distance gradients that had not been
resolved. Finally, we investigate the global halo photometric metallicity
distribution and surface brightness profile using the NB515-selected halo
stars. We find that the surface brightness of the metal-poor and metal-rich
halo populations, and the all population can be fitted to a power-law profile
with an index of $\alpha = -1.65 \pm 0.02$, $-2.82\pm0.01$, and $-2.44\pm0.01$,
respectively. In contrast to the relative smoothness of the halo profile, its
photometric metallicity distribution appears to be spatially non-uniform with
nonmonotonic trends with radius, suggesting that the halo population had
insufficient time to dynamically homogenize the accreted populations.
