Against Corps Rules

The twenty-first episode gives the Lower Rank Five a tragic backstory. Born frail, Rui was offered strength by Muzan Kibutsuji but lost the ability to walk in sunlight and had to feed on people. After his parents tried to kill him, he killed them, only realizing too late that their bond had been genuine. His fading body reaches toward Tanjiro, whose gentle touch lets the demon feel warmth before he passes on. The present-day plot then sees Giyu shield Nezuko from Shinobu while the wounded slayers are gathered and Tanjiro is brought before the Hashira.

Rui's past

A flashback shows the chronically ill boy whom Muzan transforms. His horrified parents eventually attempt to end his life; he kills them in retaliation, then learns from his mother's last words and his father's vow to die alongside him that their love was real. Muzan twists the truth so Rui can bear the guilt.

Compassion and conflict

Tanjiro detects the demon's overwhelming grief and refuses to let Giyu trample Rui's remains, arguing demons are pitiable rather than monstrous. Shinobu then darts in to kill Nezuko, but Giyu blocks her blade, citing something that happened two years earlier.

Taken into custody

Tanjiro flees with Nezuko as Kakushi treat the poisoned slayers. Kanao Tsuyuri pursues and downs him, but a Kasugai Crow relays orders from headquarters to capture the siblings alive. Giyu and Shinobu sheathe their swords, and Tanjiro is carried off to be brought before the Hashira.

The episode adapts chapters 43 and 44 and is named for chapter 44. The first eyecatcher recreates the cover of chapter 43. The scene of a human Rui trying to walk outside in the snow is original to the anime, as is the extended clash between Giyu and Shinobu. The adaptation also lengthens the Kakushi treating the wounded, and the Final Selection survivor swings at the shrinking Nezuko rather than merely chasing her.