  We report a determination of the CKM angle $\phi_{3}$, also known as
$\gamma$, from a combination of measurements using samples of up to
711~fb$^{-1}$ from the Belle experiment and up to 362~fb$^{-1}$ from the Belle
II experiment. We combine results from analyses of $B^+\to DK^+, B^+\to
D\pi^+$, and $B^+ \to D^{*}K^+$ decays, where $D$ is an admixture of $D^0$ and
$\overline{D}{}^{0}$ mesons, in a likelihood fit to obtain $\phi_{3} =
(78.6^{+7.2}_{-7.3})^{\circ}$. We also briefly discuss the interpretation of
this result.
