We report on an ongoing study on the interplay between Roberge-Weiss (RW)
and chiral transitions in simulations of (2+1)-flavor QCD with an imaginary chemical
potential. We established that the RW endpoint belongs to the 3-$d$, $Z_2$ universality
class when calculations are done with the Highly Improved Staggered Quark (HISQ) action
in the RW plane with physical quark masses. We also have explored a range of quark
masses corresponding to pion mass values, $m_\pi\geq40$~MeV and found that the
transition is consistent with $Z_2$ universality class. We argue that observables
that were usually used to determine the chiral phase transition temperature, e.g.
the chiral condensate and chiral susceptibility, are sensitive to the RW transition
and are energy-like observables for the $Z_2$ transition, contrary to the
magnetic-like (order parameter) behavior at vanishing chemical potential. Moreover
the calculations performed at $m_\pi\sim40$~MeV also put a stringent constraint for a
critical pion mass at zero chemical potential for a possible first-order chiral
phase transition.