  This paper explores the effects of changes in matter density profiles on
neutrino oscillation probabilities, and whether these could potentially be seen
by the future Hyper-Kamiokande long-baseline oscillation experiment (T2HK). The
analysis is extended to include the possibility of having an additional
detector in Korea (T2HKK). In both cases, we find that these effects will be
immeasurable, as the magnitudes of the changes in the oscillation probabilities
induced in all density profile scenarios considered here remain smaller than
the estimated experimental sensitivity to the oscillation probabilities of each
experiment, for both appearance and disappearance channels. Therefore, we
conclude that using a constant density profile is sufficient for both the T2HK
and T2HKK experiments.
