Cruelty

The premiere of the Kimetsu no Yaiba anime introduces Tanjiro Kamado, the eldest son of a poor but loving family living in the snowy mountains during the Taisho period. After a day selling charcoal in town and a night spent at a neighbor's home because of warnings about demons, he comes back to discover his relatives murdered. His sister Nezuko alone clings to life, but she has transformed into a demon and attacks him. The swordsman Giyu Tomioka arrives intending to slay her, setting Tanjiro on the path that defines the series.

A family lost

Tanjiro spends the day helping townsfolk and is kept overnight by the old man Saburo, who cautions that demons roam the dark and that this is why demon slayers exist. At dawn Tanjiro nears his house, smells blood, and finds his mother and siblings dead. He carries Nezuko down the mountain because her body is still warm.

Nezuko's transformation

On the slope Nezuko convulses, grows in size, and lunges at her brother. Tanjiro restrains her and, recalling Saburo's words, realizes she has become a demon. His pleading reaches her, and she weeps and stops her assault.

The swordsman's verdict

Giyu attacks, then pins Nezuko and prepares to behead her. He scolds Tanjiro for begging and warns that the weak are only ever crushed. When Nezuko shields her unconscious brother rather than feeding, Giyu spares her, knocking her out instead. He directs Tanjiro to seek Sakonji Urokodaki at the foot of Mount Sagiri.

The opening episode adapts chapter 1 and shares its title. The brief scuffle in which Giyu realizes the siblings differ from ordinary demons is original to the adaptation, as is the moment of him nearly cutting Tanjiro's hair. In the manga Nezuko lunges from the ground before being knocked out, while the anime shows her scaling a tree and leaping down at Giyu.