  The recently discovered two-dimensional (2D) van der Waals magnet NiPS$_3$
provides a new route to examine many-body quasiparticles under 2D confinement.
Excitons are of particular interest due to their strong coupling to the
magnetic ground state in this material. Here, by using a first-principles based
approach, we find bright excitons between 1.4 eV to 1.7 eV, similar to the
sharp coherent and band edge excitons experimentally observed. Our analysis
shows that each exciton in NiPS$_3$ is composed of a combination of $d$-$d$ and
charge-transfer character, where the relative ratio of each pairing
configuration changes with exciton energy. Finally, the wave function of the
electrons and holes is revealed to be spatially separated, with electrons and
holes residing on different magnetic sublattices. This suggests a microscopic
origin of the observed strong magneto-exciton coupling.
