  We measure the $B^0$ lifetime and flavor-oscillation frequency using $B^0\to
D^{(*)-}\pi^+$ decays collected by the Belle II experiment in asymmetric-energy
$e^+e^-$ collisions produced by the SuperKEKB collider operating at the
$\Upsilon(4S)$ resonance. We fit the decay-time distribution of signal decays,
where the initial flavor is determined by identifying the flavor of the other
$B$ meson in the event. The results, based on $33000$ signal decays
reconstructed in a data sample corresponding to ${190}\text{fb}^{-1}$, are
$\tau_{B^0} = {1.499}\pm{0.013}\pm{0.008}\;\text{ps}$, $\Delta m_d =
{0.516}\pm{0.008}\pm{0.005}\;\text{ps}^{-1}$, where the first uncertainties are
statistical and the second are systematic. These results are consistent with
the world-average values.
