Hyper-Kamiokande will be a next-generation underground water Cherenkov detector with a total (fiducial) mass of 0.99 (0.56) million metric tons, approximately 20 (25) times larger than that of Super-Kamiokande. One of the main goals of Hyper-Kamiokande is the study of CPCP asymmetry in the lepton sector using accelerator neutrino and anti-neutrino beams. In this paper, the physics potential of a long-baseline neutrino experiment using the Hyper-Kamiokande detector and a neutrino beam from the J-PARC proton synchrotron is presented. The analysis uses the framework and systematic uncertainties derived from the ongoing T2K experiment. With a total exposure of 7.5 MW ×107×107s integrated proton beam power (corresponding to 1.56×10221.56×1022 protons on target with a 30 GeV proton beam) to a 2.5∘2.5∘ off-axis neutrino beam, it is expected that the leptonic CPCP phase δCPδCP can be determined to better than 19 degrees for all possible values of δCPδCP, and CPCP violation can be established with a statistical significance of more than 3σ3σ (5σ5σ) for 76%76% (58%58%) of the δCPδCP parameter space. Using both νeνe appearance and νμνμ disappearance data, the expected 1σσ uncertainty of sin2θ23sin2⁡θ23 is 0.015(0.006) for sin2θ23=0.5(0.45)sin2⁡θ23=0.5(0.45).