In this proceeding, we report the recent studies in charmless two-body decays from $B$ factories and Belle II prospects on direct $CP$ violation in charmless $B$ decays. We present the first observation of the decay $B^0_s \to K^{0} \overline{K}^{0}$ using a dataset of 121.4 $fb^{-1}$ collected at the $\Upsilon(5S)$ resonance with the Belle detector. We also discuss the first evidence of $B^0 \to \eta\eta$. Being also related to direct $CP$ asymmetry, we present a preliminary measurement of the branching fraction and $CP$ asymmetry of $B^+ \to K^{+}K^{-}\pi^{+}$ decays. Furthermore, we discuss the future prospects on the studies of direct $CP$ violation in charmless $B$ decays at the coming Belle II experiment.