In this paper, we present the potential of the next generation neutrino experiment Hyper-Kamiokande for the study of neutrino oscillations. We first present the sensitivity of the experiment for the exclusion of the conservation of CP symmetry, and the determination of the mass hierarchy and of the octant of $\theta_{23}$ using a 187kton fiducial mass detector. We then discuss the improvements obtained with a second detector of identical fiducial mass in different configurations. With a single detector, and combining the analysis of accelerator neutrinos (295km baseline) and atmospheric neutrinos, Hyper-Kamiokande can exclude the conservation of CP symmetry in neutrino oscillations with 5$\sigma$ (resp. 3$\sigma$) significance for 57\% (resp. 74\%) of the possible true values of $\delta_{CP}$, and determine the mass hierarchy with more than 3$\sigma$ significance. This number increases to 4$\sigma$ significance if a second detector is added close to the first one in a staged approach, and to 6$\sigma$ if this additional detector is instead located in Korea, giving a longer baseline for the accelerator neutrinos.