When his parents discovered his monstrous nature, they attempted a murder-suicide to stop his sins. In a rage, Rui killed them, believing their bond was fake.
The arrival of the Hashira shifts the focus to the Demon Slayer Corps rules regarding Tanjiro and Nezuko.
The episode opens with the final moments of Rui, the Lower Rank Five demon. Kimetsu no Yaiba Episode 21
The episode ends with a bound Tanjiro waking up at the Demon Slayer Headquarters, surrounded by the elite Hashira. Demon Slayer: Kimetsu no Yaiba Episode 21 Review
, titled "Against Corps Rules," serves as the emotional conclusion to the Natagumo Mountain Arc, balancing a tragic villain backstory with high-stakes tension between the Hashira . Rui’s Tragic Backstory When his parents discovered his monstrous nature, they
Rui was born with a frail body that left him unable to walk or go outside. Muzan Kibutsuji appeared and "saved" him by turning him into a demon, giving him a powerful body at the cost of consuming humans.
The conflict is halted by a Kasugai Crow delivering orders to take Tanjiro and Nezuko into custody. The episode opens with the final moments of
Shinobu Kocho attempts to kill Nezuko, but Giyu Tomioka intervenes to protect them, violating the code he previously upheld.