The Belle II detector at the superKEKB electron-positron collider is a heavy flavour factory that started collecting data in 2019. It is expected to collect a much larger dataset than its predecessor, the Belle detector. One important class of measurements at Belle II concerns measurements using B meson decays that constrain the CKM unitarity triangle. They give insights into the origin of the asymmetry between matter and anti-matter and provide a precision test of the CKM sector of the Standard Model. Another complementary way to put the Standard Model at test is to study rare, so-called penguin, decays of B mesons that are expected to be sensitive to New Physics. In the recent years, tantalizing discrepancies have been observed in these decays and a confirmation from Belle II about whether or not these discrepancies are the first sign of New Physics is much awaited. In this seminar, I will present recent Belle II results about rare decays and precision CKM measurements. Concerning the latter, I will especially focus on decay time-dependent measurements. Upcoming Belle II measurements will allow for testing the Standard Model predictions to the ultimate precision, in a complementary way to LHCb.