Mount Natagumo

The fifteenth anime episode opens the Mount Natagumo storyline. Tanjiro, Inosuke, and a reluctant Zenitsu head for a mountain swarming with spiders and threads. There they meet a panicked survivor and discover that fallen slayers are being manipulated like puppets. The hour introduces the spider demon family and the pale child who calls them his kin.

After leaving Hisa's home, the three reach Mount Natagumo at nightfall. Zenitsu refuses to climb, so Tanjiro and Inosuke press on after catching a demon's scent. They find a lone survivor who recounts how ten slayers entered the forest before turning on each other in a sudden massacre. A rattling sound heralds the corpses of dead slayers shambling forward under control, and Tanjiro realizes thin threads bind them. By slicing the threads he frees several, only to watch them recaptured by tiny spiders reattaching new lines. A white female demon, calling the victims her dolls, is behind the puppetry, and Tanjiro understands that severing strings is pointless unless the controlling demon is killed. Inosuke uses Beast Breathing's seventh form to map the forest and locate a demon on a distant boulder. High above, a pale, child-like demon named Rui warns the slayers to stay away from his family's peace. Meanwhile, at a distant shrine, Kagaya Ubuyashiki dispatches the Hashira Giyu Tomioka and Shinobu Kocho to the mountain.

Adaptation details

The episode adapts chapters twenty-eight and twenty-nine and shares its title with chapter twenty-nine.

Differences from the manga

The short cold open, in which first Zenitsu and then Inosuke pursue Tanjiro in a bid for Nezuko's affection, was invented for the anime, as was the shot of Inosuke eavesdropping from outside. The manga reveals the demon controlling the spiders earlier in the survivor's account, while the anime delays the reveal until the demons close in.