The development of a low-communication DNS method is essential to achieve DNS for high-Reynolds-number channel flows on recent massively parallel computers. We have successfully developed this low- low-communication DNS code, and by making full use of this code, we have achieved DNSs with friction Reynolds numbers (Re_τ ) of  7986  and  15950. The  DNS  results show  that  the  von  K´arm´an  constant  in  inertial  layer  κ  ≈  0.39  was  obtained  from Re_τ = 7986, while two separated logarithmic layers with different κ ≈ 0.39 and 0.41 are obtained from Re_τ = 15950.