  In the search for CP violation at the T2K and future Hyper-Kamiokande
experiments, it is crucial to reduce the present systematic uncertainties. The
current T2K near detector, ND280, reduces the uncertainties coming from the
neutrino beam and cross-section models from $11.9\%$ to $5.4\%$ in the
$\nu_{e}$ appearance channel. These residual uncertainties mostly come from
intrinsic limitations of ND280 due to its difference in target material and
angular acceptance with the far detector.\\ In order to show evidence
(subsequently observation) of the CP violation in the T2K phase-II and
Hyper-Kamiokande experiments, this paper proposes an upgrade of the ND280
detector. It uses a 3D grid scintillator structure surrounded by Time
Projecting Chambers in order to reconstruct particles with $\sim 4\pi$
acceptance.
