  We analyze a zero-dimensional correlated system with special emphasis on the
non-Hermitian point-gap topology protected by chiral symmetry. Our analysis
elucidates that correlations destroy an exceptional point on a topological
transition point which separates two topological phases in the non-interacting
case; one of them is characterized by the zero-th Chern number
$N_{0\mathrm{Ch}}=0$, and the other is characterized by $N_{0\mathrm{Ch}}=2$.
This fact implies that correlations allow to continuously connect the two
distinct topological phases in the non-interacting case without closing the
point-gap, which is analogous to the reduction of topological classifications
by correlations in Hermitian systems. Furthermore, we also discover a Mott
exceptional point, an exceptional point where only spin degrees of freedom are
involved.
