Visually, the castle is an Escher painting brought to life. Staircases lead to ceilings. Rooms hang upside down. Hallways loop infinitely, and doors open into voids of falling cubes and spinning platforms. The "Infinity" in its name refers to its fractal nature: no matter how far you run, you never reach an exit. It is a biological extension of its master, representing Muzan’s desire for complete control and his fear of mortality.
And the Demon Slayer Corps falls, once more, into the abyss.
Nezuko, who had regained her humanity during the fight, screamed and grabbed Tanjiro’s other hand. Her Blood Demon Art—now extinguished—had left her human, but her love was stronger than any technique.
Tanjiro Kamado opened his eyes to the impossible.