WARNING: The following contains spoilers for Demon Slayer: Kimetsu no Yaiba the Movie: Mugen Train.
Demon Slayer's first film has garnered heaps of praise following an already successful first season. With Mugen Train leading directly into Season 2, fans are clamoring to see the canonical film that showcases an exciting chapter of Tanjiro's Demon-slaying quest. The titular train brings a journey teeming with twists and turns -- one of which the thick-skulled Inosuke surprisingly saw coming.
Though Inosuke Hashibira isn’t always the brightest or most rational traveling companion, he’s earned a signature spot by Tanjiro’s side as a strong Demon Slayer. A combat lover, the brash beast-like fighter usually handles situations with gut reactions, often opting for the most obvious solution. That being said, Inosuke’s inclination to size the train up as an enemy ironically turned out to be spot on.
The world of Demon Slayer takes place during Taisho era Japan, with industrial changes abound. As such, Inosuke had never seen a train before the film's events -- let alone ridden on one. Stunned, he yelled, “What the hell is this creature?!” and then proceeded to start headbutting it, believing it to be “the master and ruler of this land.” Although to be fair, this was also Tanjiro’s first time seeing a train, as he credulously remarked, “This might be the guardian spirit of this land, so we shouldn’t be attacking it carelessly.”
On the surface, this moment seemed to be another instance of Inosuke’s comedic antics, conveying his animalistic perception of his environment. However, in hindsight, Inosuke’s inclination to view the train as an enemy foreshadows Mugen Train's sinister plot twist.
When Enmu, one of the main antagonists, puts everyone on the train into a deep sleep filled with happy dreams, he meant to leave the Demon Slayers vulnerable. While most of the screen time is given to Tanjiro’s dream, the film also looks into Inosuke’s -- which depicts a cartoon-like fantasy where he’s the heroic lead commanding his helpless “underlings." The dream also includes a villain, which once again happens to be the train itself, this time resembling a centipede monster.
Entrenched in their slumber, Enmu sent insomniac children in to destroy Tanjiro, Rengoku, Zenitsu and Inosuke's spiritual cores, so they never wake up again. It should be noted that Inosuke was the most perceptive of the intruder child who enters the dream, instantly chasing her down. However, Tanjiro was the first to wake himself up by cutting himself in the dream, eventually tracking down and decapitating the Enmu. However, in one of the biggest twists of the movie, the successful strike turns out to be useless, as Enmu had fused his body with the train itself.
With this reveal, the train started to come alive, each car now wriggling with fleshy tendrils controlled by Enmu -- not entirely dissimilar to Inosuke's dream. Meanwhile, the Demon’s actual head was hidden somewhere in the train’s many compartments. Tanjiro and Inosuke eventually track down Enmu's neckbone to the engine, where the two of them cut off the real head as a team. Inosuke was especially instrumental in helping Tanjiro because his boar head mask nullified Enmu’s hypnosis.
Despite his naivety, both Inosuke’s simplified view of the train in his conscious and subconscious mind proved to point him in the right direction: the train itself was the enemy. His senses alerted him to the burrowed threat long before the unforeseen twist was unveiled. Inosuke’s unintentional foresight didn’t overtly tip him off or give him a real edge against Enmu in the end. Still, it shows that his animalistic nature may not always be as short-sighted as one might initially think.