  We find that a \textit{slowly} rotating axion-modified black hole resulting
from the backreaction of an axion field on a rotating Kerr black hole can have
a \textit{D-shaped} shadow as that for a \textit{highly} counter-rotating Kerr
black hole. This attributes to the fact that the energy exchange between the
axion matter and the black hole influences the rotation of the black hole, so
the black hole angular momentum first decreases to zero and then the black hole
starts to rotate to the opposite direction. Further increasing the coupling
leads to \textit{``human-face-like" shaped} shadows and new lensing due to the
chaotic scattering, which are novel and drastically different from Kerr black
hole. Our analysis provides the first counterexample to that slowly rotating
black hole has nearly circular shadow.
