Mio has feelings for her childhood friend Arata, but can't convey her feelings. One day, as they continue their delicate relationship, the two fight over something trivial. After letting tensions settle, Mio goes to make up with him in the pouring rain. While on her way, she gets into a traffic accident. When she regains consciousness, a mysterious and unfamiliar world appears before her eyes.

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. Kimetsu no Yaiba Movie: Mugen Ressha-hen delves into the deepest corners of Tanjirou's mind, putting his resolve and commitment to duty to the test.

Sakimori Kagami plays a VRMMORPG called Arch Earth Online. He is a veteran player with the name and appearance similar to an elderly bearded wizard from a certain book about a ring. One day he purchases an appearance change item as a last resort to spend expiring currency and gets the idea of choosing what he would want to look like if his character was ever a girl. Falling asleep should have suspended the game, but Kagami wakes up still online and feels the game has has gotten a bit more realistic. Did Arch Earth Online finally get a long-awaited update?

Kohachi Inugami, a detective who specializes in the occult, arrives at a remote village in the Japanese countryside, tasked by a hostess at a local inn to investigate a string of incidents involving rotting and mutilated livestock corpses that have been appearing for seemingly no reason. While surveying, Inugami notices a peculiar young boy working in the fields. Evaded by his peers and called "Dorotabou" for his stench, the young farmhand is surprised that anybody would take an interest in him. Inugami, piqued with curiosity, enlists Dorotabou in helping him with the investigation, despite scorned looks from the villagers. Unbeknownst to Dorotabou, this investigation will reveal a strange new world to him—one of the beast-like entities known as Kemono existing in tandem with humans—along with breathing new purpose into his previously empty life. [Written by MAL Rewrite]