Kumo Oni Ani

Kumo Oni Ani is sadistic, mocking, and confident when fighting opponents affected by his poison. He takes pleasure in explaining the stages of transformation to victims, using their fear as part of his enjoyment of the battle.

He is also cowardly when confronted by an opponent capable of overcoming his abilities. His confidence depends heavily on the assumption that his poison and spider minions will incapacitate enemies before they can reach him.

Like the other members of the Spider Family, he exists beneath Rui's authority. His behavior toward outsiders is cruel, but he does not challenge the demon who created the family's hierarchy.

Kumo Oni Ani possesses enhanced demon strength, durability, regeneration, and mobility. His unusual body allows him to move effectively through the forest and operate among the webs covering Mount Natagumo.

His poison is his defining weapon. Small spider-like creatures under his control bite victims and inject venom that progressively alters their bodies. The victim experiences numbness and pain before shrinking and developing spider-like characteristics, eventually losing their original human form.

He can also spit poison directly at opponents. His Poison Sputum attack produces venom potent enough to threaten a Demon Slayer even without the prolonged transformation process caused by his spiders.

Kumo Oni Ani encounters Zenitsu Agatsuma after Zenitsu becomes separated from Tanjiro Kamado and Inosuke Hashibira on Mount Natagumo.

Zenitsu discovers numerous people who have already been transformed by the demon's poison and is then bitten himself. Kumo Oni Ani explains that the transformation will progress over a limited period, leaving Zenitsu terrified as his body begins showing symptoms.

The threat forces Zenitsu into a desperate fight despite his fear of demons and spiders. After losing consciousness from terror and exhaustion, Zenitsu uses Thunder Breathing while asleep, accelerates himself with Thunderclap and Flash: Sixfold, and decapitates Kumo Oni Ani before the poison can complete his transformation.

Rui assigns Kumo Oni Ani the role of elder brother within the Spider Family. Their relationship is artificial and based on Rui's authority rather than a genuine sibling bond.

Kumo Oni Haha and Kumo Oni Chichi occupy the supposed parental roles in the same fabricated household.

Kumo Oni Ane is assigned the role of Kumo Oni Ani's sister. Like him, she is an unrelated demon forced to participate in Rui's imitation family.

Zenitsu Agatsuma becomes Kumo Oni Ani's principal opponent after being poisoned by one of his spiders. The demon initially dismisses Zenitsu because of his panic, but Zenitsu's unconscious Thunder Breathing allows him to close the distance and decapitate him.