  This Letter presents the first measurement of event-by-event fluctuations of
the net number (difference between the particle and antiparticle
multiplicities) of multistrange hadrons $\Xi^-$ and $\overline{\Xi}^+$ and its
correlation with the net-kaon number using the data collected by the ALICE
Collaboration in pp, p$-$Pb, and Pb$-$Pb collisions at a center-of-mass energy
per nucleon pair $\sqrt{s_{\mathrm{NN}}}=5.02\ \mathrm{TeV}$. The statistical
hadronization model with a correlation over three units of rapidity between
hadrons having the same and opposite strangeness content successfully describes
the results. On the other hand, string-fragmentation models that mainly
correlate strange hadrons with opposite strange quark content over a small
rapidity range fail to describe the data.
