  CP-PACS and JLQCD Collaborations are carrying out a joint project of the 2+1
flavor full QCD with the RG-improved gauge action and the non-perturbatively
${\cal O}(a)$-improved Wilson quark action. This simulation removes quenching
effects of all three light quarks, which is the last major uncertainty in
lattice QCD. In this report we present our results for the light meson spectrum
and quark masses on a $20^3\times 40$ lattice at the lattice spacing $a\simeq
0.10$ fm.
