◆ Role in the Story (Spoilers: Mugen Train Arc and Beyond)

※This section contains significant plot details from the anime and film, including the Mugen Train Arc, Entertainment District Arc, and Swordsmith Village Arc. Proceed only if you are up to date with the series.





Infinity Train Arc
In the Infinity Train (Mugen Train) Arc, Zenitsu is placed under a sleep spell by Lower Rank One demon Enmu, along with the other Demon Slayers. What makes this scenario particularly notable is Zenitsu's dream sequence, which provides profound insight into his character.

In his dream, Zenitsu is shown living happily with Nezuko, who speaks and treats him with affection—the perfect fulfillment of his romantic desires. Despite the blissful scenario, Zenitsu somehow senses the artificial nature of the dream. His exceptional intuition and hearing allow him to detect inconsistencies others might miss.

When Tanjiro attempts to wake everyone from their dream state, Zenitsu displays remarkable mental fortitude by being one of the first to recognize the dreamworld's false nature and wake himself up. This demonstrates that despite his outward cowardice, Zenitsu possesses strong mental resolve and the ability to face painful realities when necessary.

During the subsequent battle with Enmu, Zenitsu contributes to the group effort, showing improved coordination with his fellow Demon Slayers. Though the fight with Upper Rank Three Akaza is primarily handled by Flame Hashira Kyojuro Rengoku, this arc marks important growth in Zenitsu's mental fortitude and team coordination skills.

Entertainment District Arc
The Entertainment District Arc features one of Zenitsu's most humorous moments when he's forced to disguise himself as a female attendant at a brothel as part of a mission with Sound Hashira Tengen Uzui. Despite his complaints, he commits to the role with surprising dedication, showcasing his adaptability.

When separated from the others, Zenitsu displays increased independence, managing a dangerous undercover mission despite his fears. He encounters Upper Rank Six demon Daki (one of the siblings comprising Upper Rank Six), showing remarkable courage by standing his ground against an opponent far beyond his previous experience.

In the climactic battle against Daki and Gyutaro, Zenitsu performs Thunderclap and Flash at significantly increased speeds, demonstrating his ongoing mastery of the technique and his ability to push beyond his previous limits when those he cares about are in danger. By this point, he's developed the ability to perform multiple consecutive slashes with a single technique—evidence of his technical growth.

Swordsmith Village Arc
Although Zenitsu doesn't play a major role in the Swordsmith Village Arc (as he's absent from the main battles), this period is significant for his character development. During this time, he's implied to be continuing his training and preparation for future conflicts.

When he returns to the narrative after this arc, he shows noticeable growth in confidence and capability, suggesting that his time away from the main group was spent in meaningful self-improvement. This pattern of periodic absence followed by return with increased abilities is part of what makes his character development compelling—the audience gets to witness his growth in dramatic jumps rather than incremental steps.

Source : DemonSlayer Official