Ashiya has spent the first seven days of high school stuck in the infirmary because of a youkai attaching itself to him. He ends up asking the owner of a small tea room called the "Mononokean" for help. This is a tale involving the very morose owner of Mononokean guiding the youkai that happened to wander into this world go to the next world.
A samurai lord has bartered away his newborn son's organs to forty-eight demons in exchange for dominance on the battlefield. Yet, the abandoned infant survives thanks to a medicine man who equips him with primitive prosthetics—lethal ones with which the wronged son will use to hunt down the multitude of demons to reclaim his body one piece at a time, before confronting his father. On his journeys the young hero encounters an orphan who claims to be the greatest thief in Japan.
It is the Taisho Period in Japan. Tanjiro, a kindhearted boy who sells charcoal for a living, finds his family slaughtered by a demon. To make matters worse, his younger sister Nezuko, the sole survivor, has been transformed into a demon herself. Though devastated by this grim reality, Tanjiro resolves to become a “demon slayer” so that he can turn his sister back into a human, and kill the demon that massacred his family.
The “Seven Deadly Sins”—a group of evil knights who conspired to overthrow the kingdom of Britannia—were said to have been eradicated by the Holy Knights, although some claim that they still live. Ten years later, the Holy Knights have staged a Coup d'état and assassinated the king, becoming the new, tyrannical rulers of the kingdom. Elizabeth, the king's only daughter, sets out on a journey to find the “Seven Deadly Sins,” and to enlist their help in taking back the kingdom.
In the Japanese modern era, almost every people has forgotten about Youkai.
Ushio thinks that his father's talk of an ancient ancestor impaling a demon on a temple altar stone with the legendary Beast Spear is nuts, but when he finds the monster in his own basement, Ushio has to take another look at the family legend! To save his friends and family from the invading spirits, Ushio is forced to release Tora from his captivity. But will the creature prove to be worse than the curse?
Set at the "Death Weapon Meister Academy", the series revolves around three teams, each consisting of a weapon meister and weapon that can transform into a humanoid. Trying to make the latter a "death scythe" and thus fit for use by the academy's headmaster Shinigami, the personification of death, they must collect the souls of 99 evil humans and one witch, in that order; otherwise, they will have to start all over again.
The story follows Issei Hyōdō, a dim-witted, lecherous second-year high school student who is killed by a girl on his first date ever. Issei is reincarnated as a devil, and from that day forward, he serves as an underling of Riasu, a high-level devil who is also the prettiest girl on Issei's campus.