  The algebraic singularity method is a framework for analyzing collider events
with missing energy. It provides a way to draw out a set of singularity
variables that can catch singular features originating from the projection of
full phase space onto the observable phase space of measured particle momenta.
It is a promising approach applicable to various physics processes with missing
energy but still requires more studies for use in practice. Meanwhile, in the
double-sided decay topology with an invisible particle on each side, the
$M_{T2}$ variable has been known to be a useful collider observable for
measuring particle masses from missing energy events or setting signal regions
of collider searches. We investigate the relation between the two different
types of kinematic variables in double-sided decay topology. We find that the
singularity variables contain the $M_{T2}$ variable in many cases, although the
former is not a strict superset of the latter.
