After recovering from the mansion ordeal, the trio receives urgent orders from their crows: rush to Mount Natagumo, where Demon Slayers are vanishing without a trace. They arrive to find the entire mountain wrapped in thick spider webs, silent and suffocating. A terrified surviving slayer warns them that whatever lurks inside is beyond anything they have faced. Steel in hand and fear in heart, they step into the web covered darkness.
With the drum demon defeated, the boar masked boy suddenly turns his blades on Tanjiro, hungry for a fight with someone strong. Tanjiro answers with a mighty headbutt that flattens him on the spot. When the boar mask slips off, everyone stares in disbelief at the delicate, almost beautiful face hiding beneath it. As the group catches its breath, Nezuko steps out of her box, and Zenitsu falls hopelessly in love at first sight.
Tanjiro confronts Kyogai, the drum demon whose every beat spins the room and hurls his enemies through the air. Disoriented and battered, Tanjiro steadies himself by reading the demon’s rhythm through scent and sound alone. With one perfectly timed rising slash, he ends the former Lower Moon’s life. In Kyogai’s final moments, Tanjiro honors the forgotten writer’s dream of being recognized, granting him a warrior’s respect.
Outside the mansion, a demon with a monstrously long tongue corners Zenitsu and the frightened children. Zenitsu screams and trembles as always, until fear knocks him clean unconscious. In his sleep, the coward vanishes and a master awakens, unleashing a single blinding Thunder Breathing strike that cuts the demon down instantly. Inside, Tanjiro and the boar masked boy press deeper toward the drummer behind it all.
Tanjiro and Zenitsu reach the looming tsuzumi mansion, where two terrified children wait outside, their brother already swallowed by the cursed house. Zenitsu stays behind to guard the children and Nezuko’s box while Tanjiro steps inside. Within, every beat of a distant drum twists the mansion’s rooms into a shifting maze. Deep in the corridors, Tanjiro runs into a wild boy wearing a boar’s head, charging headfirst into danger.
On the road to his next mission, Tanjiro crosses paths with Zenitsu Agatsuma, a tearful blond boy who wails about his misfortunes at the top of his lungs. Despite his constant crying and panic, Zenitsu is also a Demon Slayer who survived the Final Selection. He latches onto Tanjiro like a frightened child, begging for protection at every step. Together, the odd pair follows the eerie sound of a drum toward a looming mansion.
With her defeat certain, Susamaru speaks Muzan’s forbidden name, and monstrous arms erupt from her own body to crush her as punishment. Tanjiro watches in grim silence, finally understanding the terror Muzan plants in every demon’s heart. He collects her blood for Tamayo’s research while Nezuko recovers from her wounds under the doctor’s care. After a heartfelt farewell, the siblings set off once more, carrying new hope for a cure.
The battle takes a clever turn as Tanjiro stops meeting force with force and starts using the demons’ own tricks against them. He redirects Yahaba’s arrows back at their master, crushing the arrow demon under his own power. Enraged, Susamaru sprouts extra arms and hurls even more temari balls in a wild frenzy. With quick thinking replacing brute strength, Tanjiro begins to seize control of the fight.
The attackers reveal themselves as Susamaru, a wild girl hurling temari balls with bone shattering force, and Yahaba, a calm demon whose arrows bend the balls’ paths in impossible directions. Yushiro hides the clinic with his concealing art while Tanjiro faces Susamaru and Nezuko takes on Yahaba. The balls smash through walls and rooftops, turning the quiet street into a storm of debris. With every throw growing deadlier, the siblings are pushed to their very limits.
The mysterious woman introduces herself as Tamayo, a demon doctor who freed herself from Muzan’s control, along with her sharp tongued assistant Yushiro. She reveals her life’s work: creating a cure that could turn demons, even Nezuko, back into humans. To finish her research, she needs Tanjiro to collect blood from demons closely tied to Muzan, and he agrees without hesitation. Just as hope takes shape, deadly temari balls crash through the clinic walls, hurled by two of Muzan’s servants.
