This Is Bad!

Having walked into the dispute between Rui and the Daughter, Tanjiro asks why Rui would hurt his own kin. Rui claims they are family, not mere acquaintances, and threatens to cut Tanjiro apart for interfering. Tanjiro counters that all bonds are precious, blood-related or not, and that friendship is no less genuine. He says that while a true bond gives off a certain scent, all he detects between Rui and the Daughter is fear, hatred, and revulsion, and he bluntly calls their connection fake.

A lone Demon Slayer arrives and, seeing what he takes for an easy kill, warns Tanjiro off, hoping the kill will raise his rank and pay. He charges Rui despite Tanjiro's warning, and Rui flicks a thread that slices the man to pieces. Witnessing Rui's terrifying speed and rage, Tanjiro grips his blade, knowing he must defeat the demon before he can return to Inosuke, then stubbornly repeats that the bond between Rui and the Daughter is false.

Elsewhere, Inosuke hides behind a tree, scrambling for a plan against Father. When the tree is smashed apart, he runs, then catches himself relying on Tanjiro and turns his anger into a charge, managing to cut through the demon's arms. Elated by his new strength, he gives chase as Father flees, only to watch the giant tremble and molt into a larger, more menacing body. Inosuke can only stare in frozen fear as the transformed demon drops down to face him.

Tanjiro openly challenges the false bonds Rui imposes on the spider clan, escalating their confrontation. He prepares to face Rui directly.

Inosuke battles the Father of the Spider Family alone and succeeds in cutting his arms, but Father then metamorphoses into a far stronger form.

This Mount Natagumo Arc chapter was adapted in Episode 18 of the anime. It deepens the thematic conflict between genuine and coerced family bonds that defines the Rui storyline.

Inosuke's brief triumph and sudden terror underscore the danger of fighting the spider clan without support, reinforcing Tanjiro's promise to return to him.