The war

Demon Slayer: Kimetsu no Yaiba – The Movie: Infinity Castle (Part 1), the Demon Slayer Corps is ambushed and dragged into Muzan's shifting dimensional fortress, setting off a wave of brutal, high-stakes battles: Demon Slayer Infinity Castle Arc Part 1 Explained Major Fights and Plot Events • The Fall into the Castle: After Muzan kills Master Kagaya Ubuyashiki, the surviving Hashira and Tanjiro are plunged into the Infinity Castle, an ever-shifting, multi-dimensional labyrinth controlled by the Biwa demon, Nakime. • Shinobu vs. Doma (Upper Rank Two): Shinobu Kocho confronts Doma, the demon who murdered her sister, Kanae. She attacks him using her Insect Breathing and wisteria poison, but she is ultimately killed by Doma. However, her sacrifice sets up Kanao and Inosuke's ensuing battle (resolved via her lingering wisteria poison). • Zenitsu vs. Kaigaku (Upper Rank Six): Zenitsu faces his former senior, Kaigaku, who turned into a demon and caused their master to commit seppuku. Zenitsu invents and unleashes a brand-new, exclusive secret technique—the Thunder Breathing Seventh Form: Honoikazuchi no Kami—decapitating Kaigaku before collapsing from exhaustion and getting rescued by Yushiro. • Tanjiro & Giyu vs. Akaza (Upper Rank Three): Tanjiro and Water Hashira Giyu Tomioka battle Akaza (who previously killed Rengoku in Mugen Train). After a grueling fight where both Tanjiro and Giyu push past their limits, they manage to decapitate Akaza. Akaza recalls his human memories and chooses to kill himself rather than regenerate. • Muzan's State: While the corps battles the Upper Ranks, Muzan Kibutsuji recuperates inside a fleshy cocoon while absorbing Lady Tamayo, as Tamayo's drug works to sap his strength and revert him into a human.