Tanjiro is tasked with delivering the Flame Hashira’s final words to the Rengoku household. How did Rengoku’s Dad react to his death?
Rengoku’s Dad decides to react to his death with anger. He disrespects Rengoku’s swordsmanship, but ultimately admits he was coping with his son’s death by acting mean and abrasive.
The father pens Tanjiro a letter explaining his reaction to Rengoku’s death.
Rengoku’s Dad reacts to his death with disrespect
In chapter #68, Tanjiro is approached by Rengoku’s father, Shinjuro. Tanjiro travels to the Rengoku household to deliver the Flame Hashira’s last messages to his family. The young demon slayer witnesses Rengoku’s final moments, who was able to smile when he died. He’s greeted by Rengoku’s brother, Senjuro, before the father interrupts.
Rengoku’s father says that a person’s capabilities and limitations are set at birth. Few enter the world with natural talent, and the rest are just of no value. The father says that because Rengoku has no talent as a swordsman, it was obvious he was going to die.
The father then reprimands Senjuro for crying, saying that the “funeral is over.” Tanjiro and Rengoku’s father have a physical confrontation that involves Tanjiro smacking him with a headbutt.
Senjuro gives Rengoku’s message to their father
In chapter #69, Senjuro approaches his father to deliver Rengoku’s last message. The father is angry, saying that Rengoku’s last words were surely a complaint about him.
Senjuro recalls Rengoku’s final message to his father, which simply asks for the father to take care of himself. Rengoku’s father then bursts into tears, no longer able to pretend that he doesn’t miss his eldest son and feel pain over his death.
The father explains his true feelings
In chapter #81, Rengoku’s father pens an apology letter for Tanjiro. He apologizes for his behavior on their first meeting. Rengoku’s father explains he was wallowing in his own self pity over incompetence, all-the-while his wife was passing away of sickness. He copes with both these issues by drowning himself in sake. That coping mechanism manifests itself again after Rengoku’s death.
So that’s the answer. Rengoku’s Dad chooses to react to his death with anger, saying that Rengoku was never a great swordsman. He admits later that he was coping with his son’s death by drinking sake and being abrasive.