The Nansei Archipelago was explored to collect wild Ceratotropis species, which are considered to be a wide range of gene(s) sources of cultivated Ceratotropis species such as azuki bean and mungbean. During the exploration, 12 accessions of Vigna riukiuensis and 4 accessions of V. reflexo-pilosa were collected. Evaluation the resistance of these species against the infestation with bruchid beetles was then conducted. V. riukiuensis showed higher levels of resistance against Callosobruchus maculatus (cowpea weevil), while V. reflexo-pilosa exhibited higher levels of resistance to C. chinensis (azuki bean weevil) compared with azuki bean. Therefore, these wild species were considered to be useful gene(s) sources of bruchid resistance for the breeding of azuki bean. In addition to these wild species, rice bean was found to show extremely high levels of resistance to both C. maculatus and C. chinensis. Gene(s) transfer from rice bean to azuki bean has not been successful due to the difficulty of producing interspecific hybrids and sterility of the hybrids. However, since V. riukiuensis could be crossed with both azuki bean and rice bean, it was considered that V. riukiuensis could become a bridge species for the incorporation of bruchid resistance gene(s) of rice bean into azuki bean.