Kyojuro Rengoku/Synopsis

Functional Recovery Training Arc
Kyojuro is present with his fellow Pillars when Tanjiro Kamado awakens.

Shinobu Kocho notes that Tanjiro is on trial, which Kyojuro sees no need for as he was protecting a Demon, which is a clear violation of conduct; he states that it was a matter they could deal with themselves. He then agrees with Gyomei Himejima's idea to kill Nezuko Kamado, witnessing shortly afterward Tanjiro's coughing fit, and remains silent when Mitsuri Kanroji asks if they should be dealing with their subordinate's trial without Oyakata-sama's input. After Tanjiro headbutts Sanemi Shinazugawa, Kyojuro looks at Mitsuri when she laughs with a neutral expression.

Demon Train Arc
Kyojuro is sent to ride the infinity train after a number of Demon Slayers who were sent there to investigate it fell silent.

As he sits on the train, waiting for it to take off and devouring his eleventh bento box while shouting "tasty," Tanjiro, who'd heard that he was going to be there and consequently followed him along with Inosuke Hashibira, Zenitsu Agatsuma and Nezuko in order to ask him about Dance of the Fire God, comes up behind Kyojuro. After the Pillar finishes his food and Tanjiro explains his question, Kyojuro energetically answers that he doesn't know what Dance of the Fire God is and that this is his first time hearing about it. He says that he's delighted that Tanjiro applied his father's dance to his fighting style, then swiftly changes the subject and tells Tanjiro that he should become his Tsuguko. Tanjiro tells him to slow down and asks if he can at least try and help a little more to answer his question.

Kyojuro says that Breath of Flames has a long history, and says that there has always been a Pillar in every age who uses Breath of Water and one who uses Flames. He explains that the other Breath Styles were derived from either those two or Breath of Wind, Stone or Thunder. Kyojuro then asks Tanjiro what color his Nichirin Blade is, to which the latter responds that it's black, and Kyojuro laughs out and says that that must be unfortunate. Tanjiro asks why that is, and, as the train starts to take off, Kyojuro explains that he's simply never seen a swordsman with a black blade become a Pillar before, and that he's heard people whose blades turn black don't even know which Breath Style to master. Seeing Tanjiro's face, he tells him not to worry and that he'll train him up back at his house.

Inosuke sticks his head out of the train's window, and Zenitsu tells him to get back inside because it's dangerous for him, and Kyojuro agrees, since he doesn't know when the Demon is going to appear. Zenitsu is shocked by this, and Kyojuro explains the situation and the disappearances of the Demon Slayers sent to investigate the train. Zenitsu starts screaming that he wants to get off the train.

The conductor then comes over to the four of them to stamp their tickets. Tanjiro smells something bad, and Kyojuro appears to sense it too as he asks the conductor to step aside as he draws his sword. A large Demon appears at the other end of the carriage, and Kyojuro asks it if it was hiding its Blood Demon Techniques as he found it hard to notice its presence, before darting forward to behead it with his Breath of Flames: Sea of Fire. The Demon's body falls to the floor, and Tanjiro, Inosuke and Zenitsu all crowd Kyojuro, praising his swordsmanship and pestering him to let them become his disciples. The Pillar enthusiastically agrees and says that he'll look after all of them.

Sometime later, when the four are all asleep, Kyojuro dreams that he's back at his house, telling his father, Shinjuro Rengoku, about his promotion to Pillarship. Shinjuro dismisses him, saying it's pointless and doesn't matter because neither Kyojuro or himself will ever become great people anyway. Kyojuro gets up and walks out of the house, out into the garden, his little brother, Senjuro Rengoku, coming to greet him and asking if their father was happy about the news and wondering if he would acknowledge him too if he also becomes a Pillar. Kyojuro remembers how his father used to be, a happy man who was passionate about training his children as swordsmen, and how he changed after their mother's death. He admits to his brother that Shinjuro wasn't happy to hear the news, but enthusiastically adds that Kyojuro's passion won't die because of that and that he'll never be disheartened. Senjuro still looks upset, but his big brother comforts him, saying Senjuro's not like him because he has an older brother to look out for him. He reassures him that whatever path he takes, he'll be a wonderful person, and, as Kyojuro hugs his brother, he tells him to do his best and keep on living, no matter what.