  We construct an equation of state (EOS) for neutron stars by interpolating
hadronic EOS at low density and quark EOS at high density. A hadronic model
based on the parity doublet structure is used for hadronic matter and a quark
model of Nambu--Jona-Lasinio type is for quark matter. We assume crossover
between hadronic matter and quark matter in the the color-flavor locked phase.
The nucleon mass of the parity doublet model has a mass associated with the
chiral symmetry breaking, and a chiral invariant mass $m_0$ which is
insensitive to the chiral condensate. The value of $m_0$ affects the nuclear
EOSs at low density, and has strong correlations with the radii of neutron
stars. Using the constraint to the radius obtained by LIGO-Virgo and NICER, we
find that $m_0$ is restricted as $600\,\mathrm{MeV}\lesssim m_0 \lesssim
900\,\mathrm{MeV}$.
