  The precise measurement of the CKM angle $\phi_3$ is important to further
test the Standard Model description of $CP$ violation. The small values of the
branching fractions of the decays involved in the measurement limits the
precision, hence a larger dataset has to be accumulated to improve the
precision. The Belle~II experiment at the SuperKEKB asymmetric-energy $e^+e^-$
collider aims to collect 50~ab$^{-1}$ of data, a factor of 50 more than that of
its predecessor Belle. The accelerator has been successfully commissioned in
2016 and the first physics collisions were recorded in April 2018. The best
sensitivity to $\phi_3$ can be achieved by harnessing all possible final states
of $B \to D^{(*)}K^{(*)}$ decays. With the full dataset, Belle~II is expected
to achieve a precision of 1$^{\circ}$ for the angle $\phi_3$. The expected
sensitivities and rediscoveries from 2018 data are presented here.
