  In this paper, we examine the effect of dark matter to a Kerr black hole of
mass $m$. The metric is derived using the Newman-Janis algorithm, where the
seed metric originates from the Schwarzschild black hole surrounded by a
spherical shell of dark matter with mass $M$ and thickness $\Delta r_{s}$. The
seed metric is also described in terms of a piecewise mass function with three
different conditions. Specializing in the non-trivial case where the observer
resides inside the dark matter shell, we analyzed how the effective mass of the
black hole environment affects the basic black hole properties. A high
concentration of dark matter near the rotating black hole is needed to have
considerable deviations on the horizons, ergosphere, and photonsphere radius.
The time-like geodesic, however, shows more sensitivity to deviation even at
very low dark matter density. Further, the location of energy extraction via
the Penrose process is also shown to remain unchanged. With how the dark matter
distribution is described in the mass function, and the complexity of how the
shadow radius is defined for a Kerr black hole, deriving an analytic expression
for $\Delta r_{s}$ as a condition for notable dark matter effects to occur
remains inconvenient.
