A memory from Rui's past reveals that he was a frail child since birth, and would always have difficulty performing physical activities, leaving him bedridden. On one night, Muzan Kibutsuji appeared at his home and offered to save Rui by transforming him into a demon. Following his transformation, Rui had regained his strength, however he could not go into the sun and had developed an appetite for human flesh.
After his parent's discovered that had killed someone, they attempted to kill him as he distinctly remembers his mother's failure to try to protect him from his father. However before they could do so, he killed both of his parents. Rui was disappointed by his parents decision to kill him rather then protect him as parents should, but as his mother laid dying on the floor, she apologized for failing to give him a healthy body. Rui stared at her in shock as he realized his parents had planned to kill him and then themselves in order to share his sin of killing someone. He realizes that the familial bond he had shared with his parents was genuine, and that he was responsible for severing that tie.
Despite the fact that Muzan had tried to encourage Rui, he could not forget that he was to blame for their deaths, and missed them deeply. Rui's headless body begins to disintegrate as he approaches the Kamado siblings, and sorrowfully tries to reach them until he collapses on the ground. Tanjiro smells the sadness emitting from Rui's body and places his hand on the small of his back.
Rui feels the warmth from Tanjiro's "gentle hand" and begins to remember the memories of his parents. As the last parts of his head begin to disintegrate, he begins to understand the severity of his sins and comes to realize that he will not join his parents in the afterlife. However, a hand touches Rui from behind as his parents reassure him that they'll follow him even to hell. Rui reverts back to his human appearance as he tearfully apologizes to his parents, and the family is then engulfed by flames as they pass to the afterlife.
Giyu approaches the siblings, stepping on whatever is left of Rui's body, and reminds Tanjiro to not pity Demon's even if they have the appearance of a child. His remarks anger Tanjiro who reassures him that he will not have mercy on Demons, however he makes clear that he will not belittle the Demons who regret and repent their actions stating that they were once humans as well. Tanjiro proceeds to sternly ask Giyu to remove his foot from Rui's kimono.
Before Giyu can respond to his remarks, he senses something approaching quickly from the forest and deflects an oncoming attack. The assailant is revealed to be the Insect Hashira Shinobu Kocho who cheekily questions why Giyu would deflect her attack. She sees him kneeling on the ground in front of the Kamado siblings and questions his intentions, before bluntly stating that everyone hates him.
Characters in Order of Appearance
- Muzan Kibutsuji
- Rui's Mother
- Rui's Father
- Nezuko Kamado
- Tanjiro Kamado
- Giyu Tomioka
- Shinobu Kocho
- Rui's past is revealed
- Giyu protects Tanjiro and Nezuko from Shinobu