The Infinity Castle arc is the climactic penultimate storyline of Demon Slayer: Kimetsu no Yaiba . It serves as a massive, multi-front war where the Demon Slayer Corps invades Muzan Kibutsuji’s shifting fortress for a final showdown . The Catalyst
The sky cracked open. Golden light flooded the ruins of the Infinity Castle. The remaining demons—those not slain by the Hashira—screamed as they turned to ash. Muzan tried to burrow underground, but Gyomei’s flail wrapped around his leg, Sanemi’s wind blade severed his arms, and Tanjiro drove the Nichirin sword through his neck. Demon Slayer- Kimetsu no Yaiba - Infinity Castle
"Fight him, Tanjiro!" she cried.