Senjuro Rengoku is a supporting character in the anime series: Demon Slayer: Kimetsu no Yaiba. He is the younger brother of the former Flame Hashira, Kyojuro Rengoku. Despite coming from a lineage of Flame Hashira, Senjuro does not have the swordsmanship in order to make his Nichin sword change in color, eventually he gives up on trying to follow Kyojuro’s footsteps.