  The so-called black hole shadow is not a silhouette of a black hole but an
image of a collapsing object or a white hole. Hence it is non-trivial whether
black hole shadows merge with each other when black holes coalesce with each
other. In this paper, by analyzing the null geodesic generators of the event
horizon in Kastor-Traschen spacetime which describes a coalescence of black
boles, we see that observers who will never see a merger of black hole shadows
exist.
