At this point, the name Kyojuro Rengoku is one that virtually every anime fan knows and holds to the highest esteem. One would think with the recognition Rengoku has received, he would be one of the lead protagonists in Kimetsu no Yaiba: Demon Slayer, but this is far from the truth. In fact, he only really appears during the Mugen Train arc. That said, Rengoku's influence on the anime community is astounding -- and it's no wonder he was able to achieve it.
Right off the bat, his charisma is evident. He speaks loudly, directly, confidently and truthfully. His gaze is always straight and forward. Even his appearance is a testament to his fiery presence. He is the embodiment of the element of fire, full of life and passion. His conversations with Tanjiro and his friends always inspire confidence and safety, as if by simply being around him, everyone will be okay.
The 'Big Brother' in a Living Nightmare
Rengoku's willingness to help Tanjiro and Nezuko is one of the biggest things he has going for him. In the previous arc, Nezuko’s demonic struggles are completely dismissed by the other Hashira, with one of them even physically harming her. However, in the Mugen Train arc, Kyojuro believes that Nezuko is worth saving and even offers to help Tanjiro perfect the fire breathing style. He manages to show more compassion towards the Kamado siblings’ plight than even Giyu.
Obviously, the fighting prowess of the mighty flame pillar must be mentioned as well. He is shown facing off against Upper Moon Three, Akaza, while defending the train. While he ultimately loses the fight with Akaza, he is not defeated. His mastery of the flame style is evident in his powerful strokes and jabs, dealing massive damage to Akaza. When Akaza manages to gouge one of Kyojuro’s eyes out and impale him through the sternum, it barely does anything to stop the freight train that is Kyojuro’s will to fight and protect those around him. Kyojuro prevents Akaza from harming any of his comrades or any of the train passengers, completing his mission, despite Akaza’s immortality and instant regenerative healing. This is a truly remarkable feat.
Lastly, Kyojuro’s backstory allows audiences to connect with him on a more human level. His father was the former flame pillar, leaving him with very large shoes to fill, coupled with the emotional abuse and neglect imposed upon him by said father. He also had to protect, and essentially raise his little brother in his father’s stead. Through all of this, he remained upbeat and determined, never allowing his trauma to define his actions.
It doesn't take much to explain why Kyojuro Rengoku has become many a Demon Slayer fan’s favorite character. The man is the embodiment of all the positive traits that make up a strong leader and good person. His loss continues to be felt by the anime community and will no doubt be felt as the anime continues into ensuing arcs.