The father of the late Kyojuro Rengoku, Shinjuro Rengoku was the former Flame Hashira. In his prime, Shinjuro was a well respected Hashira but after the tragic loss of his wife, he lost himself and turned to a life of alcoholism and bitterness. He quit the Demon Slayer Corp and even stopped being a good father to his sons, Kyojuro and Senjuro.