After a string of mysterious disappearances begin to plague a train, the Demon Slayer Corps' multiple attempts to remedy the problem prove fruitless. To prevent further casualties, the Flame Pillar, Kyoujurou Rengoku, takes it upon himself to eliminate the threat. Accompanying him are some of the Corps' most promising new blood: Tanjirou Kamado, Zenitsu Agatsuma, and Inosuke Hashibira, who all hope to witness the fiery feats of this model demon slayer firsthand.

Unbeknownst to them, the demonic forces responsible for the disappearances have already put their sinister plan in motion. Under this demonic presence, the group must muster every ounce of their willpower and draw their swords to save all two hundred passengers onboard. As things begin to spiral out of control, Tanjirou's resolve and commitment to duty are put to the test.

The worldwide box office total for Kimetsu no Yaiba Movie: Mugen Ressha-hen is over $503 million from more than 41 million tickets sold, making it the highest-grossing film of 2020 as well as the highest-grossing anime and Japanese film of all time. It was the first time in the history of cinema that a non-Hollywood production topped the annual worldwide box office. It also became the highest-grossing R-rated animated film of all time.