  About 80\% of the mass of the present Universe is made up of the unknown
(dark matter), while the rest is made up of ordinary matter. It is a very
intriguing question why the {\it mass} densities of dark matter and ordinary
matter (mainly baryons) are close to each other. It may be hinting the identity
of dark matter and furthermore structure of a dark sector. A mirrored world
provides a natural explanation to this puzzle. On the other hand, if
mirror-symmetry breaking scale is low, it tends to cause cosmological problems.
In this letter, we propose a mirrored unification framework, which breaks
mirror-symmetry at the grand unified scale, but still addresses the puzzle. The
dark matter mass is strongly related with the dynamical scale of QCD, which
explains the closeness of the dark matter and baryon masses.
Intermediate-energy portal interactions share the generated asymmetry between
the visible and dark sectors. Furthermore, our framework is safe from
cosmological issues by providing low-energy portal interactions to release the
superfluous entropy of the dark sector into the visible sector.
