  The asymmetric dark matter (ADM) scenario solves the baryon-dark matter
coincidence problem when the dark matter (DM) mass is of $\mathcal{O}(1)$GeV.
Composite ADM models based on QCD-like strong dynamics are particularly
motivated since the strong dynamics naturally provides the DM mass of
$\mathcal{O}(1)$GeV and the large annihilation cross-section simultaneously. In
those models, the sub-GeV dark photon often plays an essential role in
transferring the excessive entropy in the dark sector into the visible sector,
i.e., the Standard Model sector. This paper constructs a chiral composite ADM
model where the $U(1)_D$ gauge symmetry is embedded into the chiral flavor
symmetry. Due to the dynamical breaking of the chiral flavor symmetry, the
model naturally provides the masses of the dark photon and the dark pions in
the sub-GeV range, both of which play crucial roles for a successful ADM model.
