  We present spin-independent and spin-spin interquark potentials for the
charmonium and charmed-strange mesons, which are calculated in 2+1 flavor
lattice QCD simulations using the PACS-CS gauge configurations generated at the
lightest pion mass ($M_\pi \approx 156(7)$~MeV) with a lattice cutoff of
$a^{-1}\approx 2.2$ GeV and a spatial volume of $(3~{\rm fm})^3$. For the charm
quark, we use a relativistic heavy quark (RHQ) action with fine tuned RHQ
parameters, which closely reproduce both the experimental spin-averaged mass
and hyper-fine splitting of the $1S$ charmonium. The interquark potential and
the quark kinetic mass, both of which are key ingredients within the potential
description of heavy-heavy and heavy-light mesons, are determined from the
equal-time Bethe-Salpeter (BS) amplitude. The charmonium potentials are
obtained from the BS wave function of $1S$ charmonia ($\eta_c$ and $J/\psi$
mesons), while the charmed-strange potential are calculated from the $D_s$ and
$D_s^{\ast}$ heavy-light mesons. We then use resulting potentials and quark
masses as purely theoretical inputs so as to solve the nonrelativistic
Schr\"odinger equation for calculating accessible energy levels of charmonium
and charmed-strange mesons without unknown parameters. The resultant spectra
below the $D\bar{D}$ and $DK$ thresholds excellently agree with
well-established experimental data.
