The devastation of the Mugen Train incident still weighs heavily on the members of the Demon Slayer Corps. Despite being given time to recover, life must go on, as the wicked never sleep: a vicious demon is terrorizing the alluring women of the Yoshiwara Entertainment District. The Sound Hashira, Tengen Uzui, and his three wives are on the case. However, when he soon loses contact with his spouses, Tengen fears the worst and enlists the help of Tanjirou Kamado, Zenitsu Agatsuma, and Inosuke Hashibira to infiltrate the district's most prominent houses and locate the depraved Upper Rank Demon.

Despite being bullied, scorned, and oppressed all of his life, a 34-year-old shut-in still found the resolve to attempt something heroic—only for it to end in a tragic accident. But in a twist of fate, he awakens in another world as Rudeus Greyrat, starting life again as a baby born to two loving parents. Preserving his memories and knowledge from his previous life, Rudeus quickly adapts to his new environment. With the mind of a grown adult, he starts to display magical talent that exceeds all expectations, honing his skill with the help of a mage named Roxy Migurdia. Rudeus learns swordplay from his father, Paul, and meets Sylphiette, a girl his age who quickly becomes his closest friend. As Rudeus' second chance at life begins, he tries to make the most of his new opportunity while conquering his traumatic past. And perhaps, one day, he may find the one thing he could not find in his old world—love.

After the mysterious mana calamity, Rudeus Greyrat and his fierce student Eris Boreas Greyrat are teleported to the Demon Continent. There, they team up with their newfound companion Ruijerd Supardia—the former leader of the Superd's Warrior group—to form Dead End, a successful adventurer party. Making a name for themselves, the trio journeys across the continent to make their way back home to Fittoa. Following the advice he received from the faceless god Hitogami, Rudeus saves Kishirika Kishirisu, the Great Emperor of the Demon World, who rewards him by granting him a strange power. Now, as Rudeus masters the powerful ability that offers a number of new opportunities, it might prove to be more than what he bargained for when unexpected dangers threaten to hinder their travels.

Thirty years ago, the Eurasian continent was devastated by a supermassive spatial quake—a phenomenon involving space vibrations of unknown origin—resulting in the deaths of over 150 million people. Since then, these quakes have been plaguing the world intermittently, albeit on a lighter scale. Shidou Itsuka is a seemingly average high school student who lives with his younger sister, Kotori. When an imminent spatial quake threatens the safety of Tengu City, he rushes to save her, only to be caught in the resulting eruption. He discovers a mysterious girl at its source, who is revealed to be a Spirit, an otherworldly entity whose appearance triggers a spatial quake. Soon after, he becomes embroiled in a skirmish between the girl and the Anti-Spirit Team, a ruthless strike force with the goal of annihilating Spirits. However, there is a third party that believes in saving the spirits: Ratatoskr, which surprisingly is commanded by Shidou's little sister! Kotori forcibly recruits Shidou after the clash, presenting to him an alternative method of dealing with the danger posed by the Spirits—make them fall in love with him. Now, the fate of the world rests on his dating prowess, as he seeks out Spirits in order to charm them.