We present the results of a survey of the brightest UV-selected galaxies in protoclusters at z ∼ 4 from HSC-SSP, which are likely to be progenitors of BCGs (proto-BCGs). We select 63 proto-BCG candidates and compare their properties with those of other galaxies. Proto-BCG candidates and their surrounding galaxies have different rest-UV color distributions to field galaxies and other galaxies in protoclusters that do not host proto-BCGs, which suggest that they are dustier. The image stacking analysis reveals that the average effective radius of proto-BCGs is ∼ 28% larger than that of field galaxies. Also, we investigate the physical properties of some proto-BCGs from the SED fitting analysis.