  We investigate the charm quark system on 2+1 flavor PACS-CS configurations.
Calculations are performed at the lattice spacing $a^{-1}=2.194(10)$ GeV and
the spatial extent $L=2.9$ fm with O(a)-improved Wilson fermions for the light
quarks and the relativistic heavy fermion for the charm quark. Our dynamical
$ud$ and strange quark masses and valence charm quark mass are set to their
physical values. A comparison of the mass spectrum and decay constants with
experiments is presented. Our results for the charm quark mass and CKM matrix
elements are also reported.
