Demon Slayer: How Does The Infinity Castle Work?

Pavas Gagneja
Apr 19
3 min read

How Does Infinity Castle Work in Demon Slayer

The Infinity Castle in Demon Slayer is the ultimate nightmare maze; a mind-bending fortress that shifts, rotates, and traps its enemies like ants in a cosmic toybox. If you’ve ever wondered how Muzan Kibutsuji hides his Demon army or why the final battle feels like it's set in a maze, the Infinity Castle is the answer. Let's break down how the does the Infinity Castle work and why it’s the perfect battleground for the Demons.

Introduced in the manga’s final arc, the Infinity Castle is the ultimate trap. Its endless halls, upside-down rooms, and teleporting doors make it impossible to navigate without Nakime’s control. For the Hashira and their allies, fighting here is the biggest challenge. But how does Infinity Castle actually work, and why did Muzan design it this way?

ALSO READ: Could Kokushibo Defeat Muzan If He Were A Demon Slayer?

Nakime: The Biwa Demon Pulling The Strings

The Infinity Castle’s secret weapon isn’t its architecture; it’s Nakime, the Upper Moon 4 Demon. Nakime’s entire existence revolves around her Biwa (a Japanese lute). Every time she plucks its strings, she can teleport anyone inside the castle to random locations, rearrange rooms like puzzle pieces, creating endless pathways or dead ends, or isolate fighters to prevent teamwork.

Nakime isn’t a frontline fighter. Instead, she sits in a hidden control room, using her Biwa to toy with invaders. Her powers make the castle feel alive, and her loyalty to Muzan is absolute.

How Does The Infinity Castle And Its Tricks Work In Demon Slayer

Where is Infinity Castle in Demon Slayer

The castle manipulates on Nakime's will, with its rooms expanding, shrinking, or multiplying endlessly, defying any sense of scale or direction. Gravity doesn't play a role here, as floors morph into walls, ceilings turn into walkable terrain, and staircases twist toward nothingness. Doors and hallways serve as portals, hurling fighters into random places without warning.

The Infinity Castle is a maze where survival depends as much on quick thinking as raw power. During the final battle, Tanjiro and the Hashira are torn apart instantly: one moment they’re together, the next Mitsuri battles Demons in a cramped dollhouse chamber while Sanemi clashes with Upper Moon 1 in a blood-drenched room.

Why Muzan Built The Infinity Castle?

Muzan isn’t into interior design: he’s into survival. Thus, the Infinity Castle serves three brutal purposes:

Hide from the Sun: As a Demon, Muzan’s biggest weakness is sunlight. The castle has no windows or exits, and no scope for even a sun ray to enter.
Divide and Conquer: By separating the Demon Slayers, Muzan and his Upper Moons can pick them off one by one. No teamwork means easier kills.
Buy Time: The castle’s maze-like structure stalls the Slayers, giving Muzan time to find Nezuko, his ultimate key to survival.

ALSO READ: Why Nezuko Is The Only Demon Who Can Survive The Sun In Demon Slayer?

It’s a genius plan, until it isn’t. The castle’s biggest flaw? It relies entirely on Nakime. Once the Slayers realize she’s the core, they target her. And if they get control over her, it is over for the Demon King.

How The Demon Slayers Beat The Castle

How did Demon Slayers beat Infinity Castle

The Demon Slayers gained a strategic advantage by outmaneuvering Muzan. Yushiro's manipulation of Nakime's vision disrupted her control over the Infinity Castle, causing chaos within its shifting corridors. Recognizing the threat, Muzan eliminated Nakime, leading to the castle's collapse and leaving him exposed without a place to hide.

This move changed everything. Destroying the Infinity Castle didn’t just break Muzan’s stronghold, it forced him out into the open, where he could no longer hide. Now, the battle turns into a race against time, with the Demon Slayers trying to hold him off until sunrise. Daylight is their best weapon, and it’s the one thing Muzan can’t survive.

Final Verdict: The Infinity Castle Is A Storytelling Masterpiece

The Infinity Castle made everything more intense. It trapped the characters, kept them under pressure, and forced them to think and fight quickly. Since Nakime controlled it, every win felt like it really mattered, and every loss felt even worse.

But the coolest part? The castle was just like Muzan. It was selfish, confusing, and only cared about keeping the Demons safe. So when it collapsed, it felt like Muzan’s whole world was falling apart too. Was it the best hideout in anime? For sure, and a perfect place for the final battle.