  We propose a novel mechanism to reproduce the observed mass hierarchy for the
scalar mesons lighter than 1 GeV (called the inverse hierarchy) regarding them
as mesons made of a quark and an anti-quark ($q\bar{q}$ mesons). The source is
provided by the SU(3)-flavor symmetry-breaking induced by U(1) axial anomaly.
In particular, the anomaly term including the explicit-chiral symmetry-breaking
plays a significant role for the light scalar meson spectrum. To be concrete,
we construct a linear sigma model for the scalar mesons of $q\bar{q}$ type
together with their pseudoscalar chiral partners, including an anomaly-induced
explicit-chiral symmetry-breaking term. We find that, due to the proposed
mechanism, the inverse hierarchy, i.e., $m\left[ a_0 (980) \right] \simeq
m\left[ f_0 (980) \right] > m \left[ K_0^\ast (700) \right] > m \left[ f_0(500)
\right]$ is indeed realized. Consequently, the quark content of $f_0 (500)$ is
dominated by the isoscalar $\bar uu+ \bar dd$ component, and $f_0 (980)$ is by
the strange quark bilinear's, $s\bar{s}$.
