Precision measurements of weak interaction parameters at Belle and Belle II

We report on $CP$ violation measurements at Belle and Belle II, focusing on improving the precision of observables sensitive to the Cabbibo-Kobayashi-Maskawa matrix parameters. We present recent measurements of the CKM unitarity angle $\phi_2 (\alpha)$ using the $B \to \pi^0 \pi^0$ and $B^0 \to \rho^+ \rho^-$ decay channels, along with the first combined $\phi_3 (\gamma)$ measurement from Belle and Belle II. Additionally, we discuss the latest determinations of the CKM matrix elements $|V_{cb}|$ and $|V_{ub}|$ through exclusive decay modes $B \to D^{(*)} \ell \nu_\ell$ and $B \to \pi \ell \nu_\ell$, respectively. These results demonstrate improved precision and remain consistent with Standard Model predictions.