Ever since the death of his father, the burden of supporting the family has fallen upon Tanjirou Kamado's shoulders. Though living impoverished on a remote mountain, the Kamado family are able to enjoy a relatively peaceful and happy life. One day, Tanjirou decides to go down to the local village to make a little money selling charcoal. On his way back, night falls, forcing Tanjirou to take shelter in the house of a strange man, who warns him of the existence of flesh-eating demons that lurk in the woods at night. When he finally arrives back home the next day, he is met with a horrifying sight—his whole family has been slaughtered. Worse still, the sole survivor is his sister Nezuko, who has been turned into a bloodthirsty demon. Consumed by rage and hatred, Tanjirou swears to avenge his family and stay by his only remaining sibling. Alongside the mysterious group calling themselves the Demon Slayer Corps, Tanjirou will do whatever it takes to slay the demons and protect the remnants of his beloved sister's humanity.

The year is 1868; English nobleman George Joestar and his son Jonathan become indebted to Dario Brando after being rescued from a carriage incident. What the Joestars don't realize, however, is that Dario had no intention of helping them; he believed they were dead and was trying to ransack their belongings. After Dario's death 12 years later, George—hoping to repay his debt—adopts his son, Dio. While he publicly fawns over his new father, Dio secretly plans to steal the Joestar fortune. His first step is to create a divide between George and Jonathan. By constantly outdoing his foster brother, Dio firmly makes his place in the Joestar family. But when Dio pushes Jonathan too far, Jonathan defeats him in a brawl. Years later, the two appear to be close friends to the outside world. But trouble brews again when George falls ill, as Jonathan suspects that Dio is somehow behind the incident—and it appears he has more tricks up his sleeve.

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 final hour of the popular virtual reality game Yggdrasil has come. However, Momonga, a powerful wizard and master of the dark guild Ainz Ooal Gown, decides to spend his last few moments in the game as the servers begin to shut down. To his surprise, despite the clock having struck midnight, Momonga is still fully conscious as his character and, moreover, the non-player characters appear to have developed personalities of their own! Confronted with this abnormal situation, Momonga commands his loyal servants to help him investigate and take control of this new world, with the hopes of figuring out what has caused this development and if there may be others in the same predicament.