Spider Family

The Spider Family is a band of demons on Mount Natagumo who share arachnid features and powers. By the time Tanjiro Kamado and his companions arrive, four members remain alongside Rui, who poses as the youngest sibling while secretly serving as both leader and the strongest of the lot. The household once held more demons, but several earlier members vanished, presumably eliminated by Rui for failing the parts he assigned them or for trying to flee.

Demons rarely cooperate, so a clan acting in concert is unusual. The so-called family has no genuine warmth at its center. Tanjiro senses only fear and revulsion radiating between them, with abuse, both physical and mental, treated as routine. Despite this, every member is formidable because Rui shares blood granted to him by Muzan, and together they inflict heavy casualties on the Demon Slayer Corps before they fall.

Rui assigns each demon a fixed position within his imitation household. The figures labeled Father and Mother are expected to die shielding the children, while the Son and Daughter must guard their younger brother no matter the cost. Rui mistakes this willingness to be sacrificed for proof of a real bond, never grasping the love that drives an actual family.

New members are brought in through a brutal initiation. Rui feeds a recruit a drop of his own blood, which painfully amplifies them and grants spider-style Blood Demon Arts resembling his own. Survivors are then reshaped to look more like him before being accepted. He keeps everyone in line through pain and intimidation, and he stages hollow rituals such as gathering them around empty dishes to mimic a shared meal, as glimpsed in the Daughter's memories.

The clan's surviving roster consists of Father, Mother, Son, Daughter, and Rui himself. The Mother controls slain and captured Demon Slayers like puppets through threads, while the Son spreads a poison that slowly turns victims into his minions. The Father is a hulking brute who sheds his skin to bulk up and regenerate.

During the Mount Natagumo arc, Tanjiro kills the Mother mercifully after she welcomes death, Zenitsu defeats the Son with his single perfected technique, and Giyu Tomioka cuts down the Father to save Inosuke. Rui remains the central threat, fighting Tanjiro and Nezuko before the Water Hashira beheads him with a single decisive strike, ending the family for good.