Top: UVLFs of galaxies at z = 4 in the field (black) and protocluster (gray) volumes. The observational measures from GOLDRUSH (Ito et al. 2020) are shown as green and red triangles. The revised measurements when protoclusters are selected similar to their approach are shown in cyan lines and shades. In protocluster environment, the overall number density is much greater. Bottom: the ratio of the protocluster-to-field UVLF indicates the excess of UV-bright galaxies. The trend is even more pronounced when protoclusters are defined as regions of enhanced surface density in smaller areas (corresponding to a cylindrical volume of 7.5 cMpc in diameter and depth).